An Interjection.
Used to express extreme excitement or approval of someone or something. Generally has no connection or relevance to the topic at hand, much like yelling "High hosilver!" amidst a discussion or debate.
This phrase was made famous by the fictional character He-Man from the animated series "He-Man and the Masters of the Universe" (1983-1985), which ran for 130 episodes and was based upon Mattel's popular toy line. During various confrontations in the show He-Man would utter "By the Power of Grayskull...I Have the Power!" which is what popularized this phrase.
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.