First and foremost, have a purpose or goal that's worthwhile. Everything we do starts with where we're coming from and where we're going. What you're describing is essentially low-level burnout. The cause of burnout is that we internally realize that our goals aren't worth the time and effort we're putting into them. The right solution is to find goals that are. This is how many people have been able to push themselves far past "burnout" levels without burning out. Because their purpose is rock solid.