No matter how hard we try to be constantly productive, we must accept that life is seasonal: there are periods of high productivity when we produce output, and then there are periods of low or nil productivity when we rest and accept input—although we must do it in a thoughtful way.
This is an inescapable fact of nature: in farming, land must be left fallow so that it can regenerate, or it will become infertile.
This reality is especially tough to accept for driven professionals who want to operate at 100% of their capacity all the time. While this can be accomplished for a period of time, denying our bodies the time they need to regenerate will eventually catch up with us, with catastrophic effects such as stress and burnout.
Only when we accept to work with our bodies, and not against them, can we truly achieve peak productivity.