It's 4 a.m., and I can't sleep. I woke up a few minutes ago somewhere between panicked and pissed off, as I realized that I'd forgotten to send along a revision on a partnership proposal yesterday. It's not that big a deal, I'm telling myself--a day won't kill anything. But I'm still scripting the damn email in my head. My brain is like a movie theater to which somebody propped open the exit door, allowing all the anxieties of the day to sneak in like 15-year-olds desperate to see an R-rated movie. It'll be nearly 6 before I manage to drift off again for a few minutes of sleep.

"What keeps you up at night?" is one of those questions you hear a lot in startup land. Like its kin--"What's your revenue model?" and "What's your unique value proposition?"--it's really more about the asking than the answer. Besides being a cliché, it's an invitation for entrepreneurial chest puffing, a chance for swagger about how dedicated you are to your enterprise. It's a question I've come to loathe, and not just because I hate clichés. Mostly it's because of the many nights I actually do find myself unable to sleep.

I first noticed the question a couple of years ago, at a dinner convened by a prominent Silicon Valley VC firm. Around the table were two dozen startup founders; we were asked to introduce ourselves and then to volunteer what keeps us up at night. At the time, Iodine (my startup) was still emerging as a notion, and it caused me no anxiety whatsoever. So I just listened as one entrepreneur after another expressed hubristic concerns about growing too fast or having to beat back would-be investors. Me, I had no such troubles.

Fast-forward to a recent night at the bar of Twenty Five Lusk, a San Francisco restaurant popular with the startup set. At my elbow, an investor was chatting with a startup dude in what was clearly an investment courtship. I was trying not to listen (really!) when the VC popped the question: "So, what keeps you up at night?" 

I couldn't help overhearing the entrepreneur's pat answer about optimizing various active-user ratios. It was a lovefest of mutual insincerity.

Of course, my annoyance is also part insecurity, because I'm all too aware of those things that really do keep me up at night. Routinely, between 3 and 4 a.m., concern over our growth rate and our burn rate and our conversion rate and every other metric starts scratching at my consciousness. Sometimes I can shoo these thoughts away and stay asleep. But most nights, my brain responds to the stimuli. I start to think. Then I think some more. Soon, a whole to-do list begins to emerge, and I tick through the items on it, one by one. There's something about the rawness of a human brain at 4 in the morning that steeps any concern in a cocktail of fear, uncertainty, and doubt. If I'm lucky, within an hour or so I'll arrive at a plan of action and conk out again.

Then, in the light of day, all my worries fall back into place, rightly framed by context and competing priorities. 

What I've learned is that sleeplessness is part of the entrepreneurial condition. There's just no escaping the all-around anxiety that comes with running a startup, brought on not only by the tenuousness of the enterprise but also by the sheer volume of tasks that crop up each day. Though my recent insomnia is partly a barometer of fear, it's a measure of effort as well. After all, when I can't do everything I need to during my waking hours, at least my brain is trying to get something accomplished in the off-hours.

So what keeps me up at night? Knowing that if I start sleeping like a baby, that's when I should really start to worry.

From the June 2015 issue of Inc. magazine