Building a new technology company is really, really hard.
In order to do it successfully, you have to sweat the details, worry about all the things that might go wrong, and suffer more than a few sleepless nights (either from working through the night or just worrying through the night).
All of those things that you go through—a boiling stomach, lack of sleep, waves of paranoia, and vivid visions of your own demise—turn out to be good things.