Burnt out is something people experience in many situations. I used to constantly get burn out periods that's why I ceased game development for now . In regards to life in general to keep on top of things both mentally and physically. I set mini goals to achieve. Mind is constantly busy and fresh with ideas. A healthy diet and adequate sleep is essential. Drink lots of water. Exercise regularly keep yourself in best possible condition. Meditation is something great for the mind even just some ambient music and close your eyes for 15 minutes or so can go a long way to refreshing your mind. You can be super productive if you are focused, healthy and inspired mentally.
I started a lifestyle regime few years ago. I have much less time now than I had years ago but I'm achieving a huge deal more. Never had a burn out since aside from a few work related physical niggles.