I find stress a pretty interesting topic of research, and there are countless books on theory, tips, psychology, etc. At the end of the day, it all boils down to the fact that our body are machines that need to be looked after and fed.
The Theory of Cumulative Stress: How to Recover When Stress Builds Up
If you want to keep your bucket full, you have two options.
Refill your bucket on a regular basis. That means catching up on sleep, making time for laughter and fun, eating enough to maintain solid energy levels, and otherwise making time for recovery.
Let the stressors in your life accumulate and drain your bucket. Once you hit empty, your body will force you to rest through injury and illness. Just like it did with my professor.