Standing firm on your word no matter what
Promised my son I'd help him build something in the garage Saturday morning. Got invited to go fishing with the guys Friday night. Almost cancelled on him for it like a coward. Then I remembered my own dad never did that to me. Went fishing another time. He's only young once and a man's word is all he really has. Worth more than a day of fish.
The garage build sounds way more memorable anyway. When he's older he's not going to remember you missed that fishing trip, but he'll remember the Saturday mornings you actually showed up for him.