When you say something is a "piece of cake," it means it is very easy to do.
In the 19th and early 20th centuries, African Americans started "cake walks." They walked or danced around a cake in pairs, and the best couple won the cake. This is how the idioms "cake walk" and "piece of cake" came about -- both meaning that something is very easy to do.
A: Hey! How did you do on the exam?
B: I got an A. The exam was a piece of cake.
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.