As much as I love my regular golf pro (Doug Acton, Your Swing's Covered), I think my favorite golf lesson came on a driving range in San Bruno.
It was my first day with my new driver, and I was hitting everything right. In the stall next to me was a Chinese man in his 70s, just striping 4-irons about 200 yards. He started watching me swing, but without saying a thing. He watched me from the side, from behind, from the other side. This went on for about five minutes. After one last swing, he took a step closer and said (with a heavy accent): "You in too big a hurry." Then he got me to slow down, and swing on an inside-out path -- and my drives started going straighter and farther.
Unfortunately, it seems to be a hard lesson for me to hang on to. What's more, it's one that applies to many areas of my life. I'm a pretty fast-moving person. But I'd probably benefit from being in a bit less of a hurry.