Startups are not the best choice for work-life balance, and that's sort of just the sad reality.
If you have several ideas that all seem pretty good, work on the one that you think about, when you're not trying to think about work.
Great execution towards a terrible idea will get you nowhere.
You should be giving out a lot of equity to your employees.
Be suspicious of any work that is not building product or getting customers.
Long term thinking is so rare anywhere, but especially in startups. This is a huge advantage if you do it.