I agree. I am an engineering professor (recently retired) and administrator or a university / industry centre of excellence. If it isn't yet another meeting, it is typing on the keyboard. I enjoy it enough to keep at it. But give me one day working on the old car and I am more refreshed that if I had a month's holiday. It doesn't have to be mechanics either; it could be fixing up a very old family homestead that any sane person would have long condemmed.

If I had to sum it up in a sentence it would be:
The only real joy in life is doing something well that you value (be it auto mechanics, teaching, administrating, family...).

Bill