Burnout is from overpressure. You might love programming but if the startup is failing, the boss is slowly going mad and you don't know what bug to fix first, love won't help you.

Or it might be entirely internal and kind of caused by your love, e.g. turning insane from your inability to focus on programming and finish anything due to undiagnosed ADHD (my case).

No pressure - no burnout, I think.