Did you ever go back and watch how many times you got lucky before that kid said something? I had a guy ask me why I never looked up when I was running a saw on a spar and it bugged me for a week. What worked for me was making the new guy the check. Now whoever I'm training has to call out my tie in and my cut plan before I fire up, and if they miss it I buy lunch. It feels dumb at first but it keeps me honest and it gets them in the habit too. Costs me about two sandwiches a month and it already caught a bad limb I would have missed. Green horns see what we stop seeing.

Buddy of mine ran a 4 pound cross peen for years on big draw jobs and swore by it until his elbow started talking to him. He dropped to a 2 pounder and said his control got way better on the finish passes, but the metal moved slower so a long session turned into a longer session. His fix was keeping both on the stand and switching when his arm told him to. Hot metal moves easier than you think, so a lighter hammer worked harder is often better than a heavy one worked tired.