A couple of weeks ago, Medium pushed out a link to an article about a highly accomplished Harvard student. One of the primary messages of the article was that smart people can manage one or more “side hustles” while also pursuing a primary career or educational path in life. This student refers to herself as a “multihyphenate,” which for her includes activism and speaking engagements in addition to being a full-time student. 

In the same week that I read this article, my wife sent me a link to a publication called The Side Hustle Bible, by Sophia Amoruso. As you read her material you clearly sense how much she has accomplished―New York Times bestselling author, awards and recognition by all the major business press, two successful startups, and even a Netflix series about her life. Much of this she accomplished before the age of 30, and she is evidently quite proud of it all. Her objective in the publication is to offer a step-by-step guide about how to pursue your side hustle. There’s no question that pursuing a new career or starting a business while engaged full-time in something else is very hard to do. Since she has successfully done it more than once, she probably is uniquely qualified to offer advice on the topic.

Both of these articles put forth–and even advocate for–a point of view that has validity. People pursue side hustles all the time. Many of them are successful. What I don’t appreciate about the articles is that they don’t even acknowledge the possibility that doing so comes at a cost. The cost is real, and it comes in multiple forms. Unless you are Elon Musk (sorry, you probably aren’t) these costs are inescapable at some level. 

Before I make my case, I must qualify what I’m about to say. I don’t consider volunteerism, community service, hobbies, exercise, investment in relationships, or continuous learning to be side hustles. They are essential parts of a healthy, mature life. I’m also pointing no finger at people who have to work more than one job just to live, or the college student who must work to pay for school or cover the expenses of life. I have had a job at some level continuously from the age of 14 to the present, uninterrupted by anything other than a stint in full-time volunteer service in Latin America. (A note to my early employers: I won’t rat you out for violating child labor laws.) Realistically, I had no choice but to do so. 

My audience here is those who intentionally, and with some dedication, pursue income from more than one line of work simultaneously in circumstances where it is not required to live. I’m now being repetitive: there is no such thing as a side hustle that does not come without a cost―especially if it is pursued with seriousness and dedication, and that cost is borne by the person who pursues it. The cost is especially high if you are young and early in your career. 

I’ll make my case here with three overall points (if you know me well, you know everything always comes in groups of three).

All outperformance happens on the margin

In any pursuit, whether it be a profession, a sport, a hobby, or some other passion, the major differences in performance happen on the margin. This is as true a universal law as gravity. The examples I could give are endless. When weight training, the vast majority of the gains in muscle mass, strength, and power come in the last one or two repetitions in a set. Stop short of those reps, and you lose those gains. Again, these aren’t small gains that are consistent with the extra reps―we’re talking about the vast majority of gains. 

As another example, I’ll compare two professional golfers, both of whom have played 57 rounds so far in 2021. One critical statistic in golf is “one-putt percentage,” which measures the frequency with which a golfer can finish a hole with a single putt after landing on the green. Cameron Smith has a one-putt percentage of 44.63 percent. Max Homa’s is 43.11 percent. Not a big difference, right? Across 57 rounds, that means that Smith finished 434 holes with one putt while Homa hit 419―that’s a 15 strokes difference. 

Again, this doesn’t seem like a huge deal, until you see the final results in golf tournaments. There are certainly times where tournaments end in blowouts with the winner beating the second place finisher by five strokes or more. Tiger Woods used to do this frequently. It can be exciting to be that dominant, but it’s not that common. It’s much more common for a tournament to be won by one or two strokes. In that light, 15 strokes difference across 57 tournaments is a very big deal indeed. 

I set a very big goal for myself when I was a sophomore in college–I wanted to attend what I believed to be the best business school in the world. I didn’t attend an elite undergraduate institution (sorry, Weber State) so I knew the odds were not in my favor. When I set that goal I made a decision: In each case when I was studying for a test in any class, I would go until I thought I was done―when I could not learn or remember more to help me ace the test―then I would study for 15 minutes more. 

I don’t believe I ever broke this rule over the next three years. I have no doubt that those extra 15 minutes, on multiple occasions, led to insights and breakthroughs during tests that meant the difference between an A and an A minus. Each A on a test contributed to an A in the course. Each A in each course contributed to a high GPA. That GPA led, against all odds, to my being admitted to the school of my dreams. I have tried to keep that habit up throughout, not only my time at my dream school, but also, in a slightly different form, in as many dimensions of my life as possible. Just a little bit more, applied consistently, means a lot more in the long term.

How does this apply to side hustles? The time you spend on the hustle takes away from something else. It is literally not possible for it not to. It may mean less sleep, missed exercise, or putting off that article you were going to read that contributes to your knowledge to do your main job. It may mean missing time with a loved one that might not mean much at present, but that over time eats away at the strength of a relationship. It may mean that in those moments where your work needs you for a last-minute deadline or something else truly urgent, you are not available. Added up over time, these missed opportunities have a cost, and it only accumulates. There is no free lunch. Ever.

Compound interest is an immutable law 

Albert Einstein is purported to have said that “the most powerful force in the universe is compound interest.” This is probably apocryphal, but it may have as much tangible relevance to you and me as the theory of general relativity.

The statement pertains to finance. Say you have $100 that earns 6 percent interest. At the end of the year, you have $106 that, again, earns 6 percent interest. In 20 years, your original $100 is worth $311 and you didn’t have to do a thing other than letting compound interest work its magic.

What’s true in finance is also true in life. Small investments on the margin contribute to a new baseline, which then can be invested in to get even more improvement. Zappos is famous for having asked their employees to think of ways that they could be one percent better every day than they were the day before. What is that worth? Nearly 38x in one year. Think about that for a minute. What would it be worth to you to be 38x better at something by improving one percent each day? 

I have a bad back. A couple of years ago I decided that one thing I could do to ameliorate the pain while I was deciding on a long-term solution would be to do planks every day. On the first night I did planks, I think I hit 45 seconds and then collapsed on the ground. Yeah. Not so great. I decided that night that my goal would be simple: I would add five seconds each night. That’s it. Five seconds doesn’t sound so hard, right? I should be able to do pretty much anything for five seconds. You know where this is going. Except for a few days per month when I just couldn’t pull it off, I added five seconds per night. That’s the law of compound interest at work, in this case for my health.

How does this relate to side hustles? Any side hustle takes time and energy. That is time and energy you could apply, even at extraordinarily small levels, to something else that you highly value, including your primary career. And those very small differences, compounded over time, can transform your performance in a primary career to levels you would have never thought possible. 

Performance is both absolute and relative

You may think, and it may be true, that your side hustle doesn’t take a lot of time. Even though you are doing it, your performance in your “real” job is perfectly good, perhaps even great. Here’s the problem: you aren’t being judged by only an absolute standard. You have peers performing in perhaps the same job, similar jobs, or in competitive companies that aren’t pursuing side hustles. 

Let’s just say, for the sake of argument, that you are veritable clones in terms of capability and commitment. Your peer with no side hustle, and therefore no distraction, will likely pull ahead of you. She will get the promotion, the recognition, the cool new assignment while you feel stalled. You may feel frustrated that your excellent work is not sufficiently recognized. Well, in the real world of early birds and worms, it’s not always true every early bird gets fed. If there aren’t an unlimited supply of worms, it pays to be the earliest.

On the day I saw the link to the article about the Harvard student I mentioned at the beginning, I decided to send out a tweet on this topic. Within minutes, one of the CEOs of a company Kickstart funded reached out to me expressing frustration that he knows of several employees in his company who pursue side hustles and their leadership team is trying to figure out what to do about it. In some cases the employees are completely open about doing it. In others they are hoping that no one notices. They do. 

In our business, we don’t invest in companies that are being led by a person or team that is pursuing it as a side hustle. No thanks. If you don’t believe in your company enough to put all of your time and attention into it, why should we? In addition, we include a clause in our investment documents by which the founder commits to us that he won’t pursue a side hustle. If you want our money, you have to commit that you are all-in. Most jobs are hard enough, especially when creating a startup. 

I’ve had dramatically different chapters in my career. In many ways, each chapter could not be more different than the one that came before. In all cases when I made the change, I was all-in. I’m now a VC. Every single thing I do professionally relates to that. If I have something else in my life, it is because I pursue it for the other dimensions of what make me human―relationships, love, personal passions, physical fitness, and health. I don’t make money–nor am I preparing myself to make money–from any other pursuit. I can’t even imagine considering the decision to do so. 

So what’s the upshot here? Clearly I’m not much of a fan of side hustles. That said, people pursue them all the time. If you’re doing one (or considering it) just know that there is no free lunch (yep, I’m repeating myself). We all make our own choices. We just don’t get to choose the consequences.