Sleep is certainly a challenge as a founder, or I would say "overworking" in general. It can be tempting to try and fix things by working more on them, and I've found personally that it rarely helps. With sleep, if I get 7.5 hours of sleep compared to 5 hours of sleep, it makes a huge difference for how much I can achieve, how focused I am. Especially the tasks that take a little more willpower (which are usually the most important ones) are the tasks that get left until tomorrow if I haven't had enough sleep.