Stress
Huge creative pressure, long hours, no job security, low pay, actor "personalities," producers staring over your shoulder, and worries about how you'll pay for retirement, health care, or even tonight's dinner. You could say there's pressure to do well, and that's before the curtain even goes up on opening night.
Good advice is to never read your reviews. Even if they're good, you'll end up with an inflated ego. And a head that big is never appropriate unless you're floating in the Macy's Day Parade.
And if the reviews are bad, there's no amount of chocolate ice cream that can fix that problem, so why bother? Everybody's a critic, especially the critics, but let's see them try to mount a production of The Wizard of Oz with actual trained flying monkeys.
In hindsight, not the best creative decision you've ever made. But you've got to stick by it, because if you're not sure of your artistic vision, you can be sure the people paying you for it won't be either.