How do I keep going when restaurant work is burning me out?

You have the discipline, that is not in question. What is wearing you down is the nature of the work itself: everything spoils, everything rushes, and the service never lets up. Discipline can carry you through a hard day, but no discipline survives forever without rest. The burnout is not weakness. It is a warning. The grind will not slow down on its own; the kitchen does not care that you are tired. So the change has to come from how you protect yourself inside it. You cannot pour out every night at full intensity and expect the tank to refill on nothing. Something has to give before you do. Pick one real recovery and guard it, a full day off you do not trade away, real sleep, one meal you eat slowly and off your feet. Small, but non-negotiable. Burnout comes from having no floor under you. Build one solid piece of rest and stand on it, so the work stops taking more than you have.