Let's say you have a stellar resume. You went to all the best schools and got flawless grades. You landed the best internships. Maybe you've even have a few years under your belt excelling at top companies.

But now you've caught the startup bug.

You look at the amazing things entrepreneurs are doing, the impact they're having, the possible payout of great success, and you've decided to make a change. You're going to take your impressive talents to start-up land and help build a fledgling company. With a background like yours, you're sure to succeed, right?

Not so fast, cautions Close.io CEO Steli Efti in a thoughful post on the company's blog. The qualities that made you such a fabulous student and successful big company employee won't necessarily help you thrive at a small, scrappy company, he insists, unless you understand one huge truth about working at a start-up.

You write the rules.

"Most people think of success as a game--play by the rules and you win. At a startup, you don't play the game, you build it," Efti explains. It's a truth, he feels, that regularly trips up overachievers when they first join a small company because it's so different from other theaters of success they may have experienced.

"School is a straightforward game. There are set goals, and a clear trajectory for success. Study hard, suck up to professors, test well, and you win. A big company is no different--there are set rules for moving up the corporate ladder. Startups don't have an existing framework for success--they create it from scratch," Efti elaborates.

Realizing that there is no playbook to follow can be deeply uncomfortable. It entails not only tolerating risk but working with a massive amount of day-to-day uncertainty. That can be particularly troubling for folks with a lot of success in more orderly environments under their belts, as many have gotten addicted to the well marked paths and steady stream of affirmation they provide. Efti quotes Neil Patel, co-founder of KISSmetrics, Crazy Egg, and Quick Sprout, on the subject:

"Experienced employees aren't better than hungry ones ... [because] what they lack is the ability to move fast and do so without relying on others. Those corporate executives are used to farming out the work instead of figuring out how to do things on their own. When a startup is young, these are the people who I recommend you stay away from."

Tips for entrepreneurs and employees

Efti goes on to offer founders a list of suggestions to ensure that the people they hire can deal with the ambiguity and messiness of start-up life, including stressing this fact in interviews, encouraging employees to take ownership of their ideas, breaking down barriers between teams, and giving new hires some skin in the game in the form of equity. If you're an entrepreneur struggling to find people who understand the chaos of life at an early-stage company, it's well worth a read in full.

If you're an individual contemplating jumping to a start-up from academia or a big corporation, the takeaway is probably simpler but scarier -- you need to think really carefully about whether you can handle the kind of environment where there is no pre-scripted path to success. Because if you can't, that start-up job almost certainly isn't for you.