Today is the 105th anniversary of Merkle's Boner, which cost the New York Giants the 1908 National League pennant. In the aftermath of the game and umpire Hank O'Day's controversial ruling, Giants hurler Christy Mathewson, the pitcher of record that fateful day, said this:
If this game goes to Chicago by any trick of argument, you can take it from me that if we lose the pennant thereby, I will never play professional base ball again.
Thankfully this was that rare occasion when the famously upstanding Mathewson, nicknamed "The Christian Gentleman," didn't keep his word. Matty went on to pitch several more seasons, leading New York to the pennant in 1911, '12, and '13.
For more on Merkle's Boner, see this terrific comic by Molly Lawless.