Staying mentally sharp while on a hunt is important. If you don't stay focused, you could end up making mistakes. Maybe it's just a small mistake, like ignoring that faint rustle of leaves behind you, not knowing it's the buck you've been waiting for all season.
Or, maybe it's a larger mistake that puts you in danger like rushing to get out of the stand and forgetting to unload your rifle before lowering it to the ground. Either way, staying fueled and focused on the hunt and your surroundings helps you avoid these kinds of errors.