I guess this is the crux really. Is burnout merely an arbitrary expression of exhaustion and overwork, which carries thoughts and resentments that may seem 'real' but are really just manifestations of stress? Or are the resentments in any way real? If they're real, I personally feel they need to be tackled in a way beyond mere coping.
With no resolution to the mismatch, it leads to self-repression of the resentment, then to cynicism, and indeed it saps away emotional energy to manage this.
So, it's important to be aware of how the job vs personal goals match. Making the job expectation known to the superiors may as well help keeping the balance. Btw, brown-nosing is a form of negotiation, sure it's not the only way.
Otherwise the burn-out will be more self-inflicted. Also, there're cases that may have no practical ways to balance (culture fit). In this case setting to oneself a limited time-frame to attempt finding the balance (improving the job goals). Then declare 'mission accomplished' and move on (taking the side of personal goals).
Low and time-wasteful work-load (9-5) may as much lead to burn-out as the sweatshop slavery kind. But both environments have those that would flourish there.
If you’ve got resentments you’ll need to work through them. Get help. Debrief your role in the causes. Regrets probably exist at first but you’ll find moving on with new is healthiest approach after you’ve worked out the details of the old.
Work on frustration tolerance. Little things should stay little. Laughter may help. Or not.
Reconnect with purpose. Find a purpose. Make it clear. Make it detailed. Plan. Execute.
You will need to change. What that means is up to you.
Check in with exercise, diet, social circles. Don’t disconnect from any of these. Fix any deficiencies.
After all that maybe you can forgive, forget and move on.