Nothing is worth risking burnout for (well, maybe saving your child or something like that). It takes ages to recover (roughly as long as you've spent building it up, which may be years), and I'm not entirely sure if it might leave anything permanent (wrt dealing with stress or pressure) preventing you from crawling back up to your previous 100%.

So, think about that and act.

How exactly to break it, I'm seeing loads of great advice in the rest of this thread so I'm not going to repeat it all. It's a different struggle for everyone.