I have a routine for when I get home from work: Crack each toe, then my ankles, both knees, pelvic bone (a particularly good one), twist-crack my lower back, both shoulders, my wrists, then each and ...

I’ve got my fair share of unconscious habits: running my hands through my hair, tapping my feet, pursing my lips when I’m concentrating—and, of course, cracking my knuckles. That last one is perhaps ...