A situation in which a team is leading a playoff series 3 games to 1 and still ends up losing the series 4-3 in 7 games. The most recent example of this is the Cleveland Indians blowing their 3-1 lead against the Chicago Cubs in the 2016 World Series. This phrase was popularized by the Golden State Warriors, after the lost in the NBA Finals to the Cleveland Cavaliers after holding a 3-1 lead.
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.