When I was three years old I was complaining to my parents about how much my thumb hurt in the winter. They told me it was because I sucked on it and so it became chapped. So I just stopped. Apparently never sucked my thumb again.
I wish I had the willpower now that I did when I was three.
oh man. that unlocked a similar memory for me. my mother showed me the calluses I was getting from sucking my thumb so I switched thumbs. as I kept getting calluses I kept switching fingers before I finally gave it up