From genius.com : "The original inspiration for the lyrics came from David Lee Roth watching a person on TV who was threatening to commit suicide by jumping off of a building and Roth figured someone in the crowd must be thinking, “Go ahead and jump”. It was, however, not written about suicide – the song is about ‘jumping’ on the opportunity to hook up with someone."
Doesn't it say "I get up and nothing gets me down"? I always thought that sentence described being motivated and not letting anyone ruin your good mood.