Chess
In high school, I ate, drank, and slept chess. At that age - 16-17 years old - with an entire lifetime stretching into the future, it is easy to imagine all curves trending upwards indefinitely. I certainly believed this would be true of my skill in chess and my ELO rating. In retrospect, 1973 may well have been my peak chess year. Playing first board for the RL Thomas chess team, I scored 8 wins, 2 draws, and 1 loss which certainly sets some kind of personal record. You can play these games, including my bone-headed loss to Goulet, below.
Rochester NY HS Team Chess League - 1973. Board 1 games.
I recently hooked up with an old HS teammate - Scott Maid. He is near USCF Master strength and handily defeated my French Defence (note: Scott is the one with the meaningless 1200 rating from chess.com.)