A guy at a Phoenix climbing gym said my belay checks were sloppy, and he was right
I had been climbing with the same partner for two years and we got lazy, half-checking knots and harnesses before every route. A stranger at the gym in Phoenix pulled me aside after I nearly lowered him with a loose strap and said "you two are gonna get someone hurt, slow it down." It stung but now we do a full verbal check every single time, so what did someone say to you that made you fix a bad habit you didn't even know you had?
Had a similar wake up call with my dad's table saw years back. He watched me rip a board with the blade guard pinned up and just said "that's how you lose fingers" real quiet, no lecture. I was 24 and thought I knew everything about woodworking. Now the guard goes back down every single cut, even when it's a pain. Nobody ever forgets the day someone points out the dumb thing you'd been doing on autopilot.