That old machinist who taught me to trust the tool over my eyes

Back in 2009 I was running a beat up Bridgeport in a shop near Tacoma, and this guy named Roy, must have been 70, came over while I was rechecking a bore for the third time. He just watched me struggle with the indicator, then said, 'The tool ain't lying, you're just scared of what it says.' He showed me how to set up a simple test cut on scrap aluminum and measure it twice before touching the good part. I was convinced my spindle was off, but it turned out my fixture had a burr the size of a grain of sand. He never said I was wrong, just handed me a file and said to knock it off. That one interaction saved me a whole afternoon and a $200 piece of stock. You ever have a grumpy older guy in the shop set you straight in a way you still use today?