What happens when founders try to sleep at night is this: their mind spins uncontrollably between scenarios that result in a glorious success and scenarios that result in a burning death crash. Most founders I know ride a fine line between seeming to be in total control and going nut balls.
All I can say is welcome to the club - you're normal!
Whenever people ask me how I make it through, I always say the same thing. Sit down and write down the storms that you are worrying about and divide them into two list. Those that are under your control and those that aren’t. Then focus on the list that you can control. If you stare at that list long enough you’ll realize a commonality. That the solution to every single one of them begins with having a team that is rock solid, one that isn't afraid of challenges and one that believes in you as a founder. If you do this one thing right, it will steady you and calm your mind enough to face and conquer any challenge.
All I can say is that it took me about 1 year to realize I was normal. Many sleepless nights, late nights, and early mornings. If you are a founding member of a startup, it should keep you up at night. If it doesn't, chances are you'll never make it. Hat tip: Ben Casnocha