I've never felt more fully alive than when I get to play "Smooth Criminal". Playing something challenging like this piece requires competency.
You simultaneously have a sense of control and effortless involvement; your sense of self vanishes, and you feel nothing because you are fully absorbed in the music.
We are most happy when we challenge ourselves and perform at our best. Happiness is found, not in mindless passivity, but in mindful challenges. The more we challenge ourselves, the happier we are while doing it.