Believe that your high can come from coding stone cold sober. I can get so freakin high from rockin on some awesome shit. I'm poppin tictacs wih spearmint gum. Last I checked? (never) they don't cause short term mem-loss...
As for start up stress - that's part of the gig you pay for trying to make a go of it. You need both of these to get through it: Fucking good friends and/or employees who have your back & seriously long term vision. Believe in what you're doing and you will succeed.