To “pull a punch” in boxing is to throw a punch with less force than what you’re capable of.
Sometimes it’s good to pull a punch. Maybe we’re experimenting with a new exercise routine, entertaining a “coffee chat” with a potential employer, or simply learning something in a foreign domain for the first time.
But for the things that really matter: pull no punches. Leave nothing in the ring.
The hard part, though, is knowing when to pull, and when to commit.