You do not seem to understand.
How to avoid burnout?
We don't. Do you get burnt out listening to your favorite music or spending time with your favorite people? No, you do it because you love it. Training, pursuing a cut or growth phase, prepping for competition, trying to get stronger, trying to improve endurance, trying to be better than yesterday - these are no different. We do it because we love it.
Do you believe in what you're doing?
A devout Catholic doesn't attend mass because they've convinced themselves it is truth, they do because they believe in their faith deep in themselves regardless of what anyone else has to say. Even without the church or a priest, they would still pray and execute their faith. Pursuing training, body goals, strength goals, etc. are no different.
Are you aware of potential downsides?
Training can be dangerous and it's an accepted risk, and we educate ourselves and take precautions to train safely. Driving can be dangerous but it's an accepted risk, and we educate ourselves and take precautions to drive safely. Using PEDs can be dangerous and it's accepted risk, and we educate ourselves and take precautions to use them safely. Some people don't, whether it's training/driving/PEDs/sex/etc, and they learn the hard way or get lucky and go unscathed.
These things have been clear by many of the responses you have received. You asking these questions presents as though you have doubt within yourself and pursue it in commitment - not in passion.