>> Some people have trouble doing meaningless intellectual pursuits like crosswords, sudoku etc.

My Dad is like this. I'm like this. My son is like this.

Unless we're busy, pushing ourselves to build something, fix something or just outside doing something we don't feel the reward.

My Dad told his motto, "A rolling rock gathers no moss - until it finally stops rolling." He told me that in his 50's - he's in his 80's still out in the garage refinishing old furniture and giving it away. The drive the man has just never burns out.