I’ve heard this my whole basketball career, and I’ve never really bought it.
I believe life is a series of sprints, not a marathon. We have spurts. It’s important to maintain a baseline standard and continually work to improve that standard. But we will all have stretches of time where we will be amazingly productive/happy/successful. I like to thrive during these periods, then rest, re-charge, read a bunch, and then go back in the trenches. Then rest, read, re-charge, and back to the trenches.
Burnout comes from staying in the trenches too long. Don’t get me wrong — to see something through requires sticking with it in the long run. I’ve been working 65 hour weeks since I was 13 and I don’t see any slowing up. In this sense, life is a marathon, but with plenty of rest stops and water breaks along the way!