do one's thing
1. To do what one does well and actually enjoys doing.
Two thousand fans paid $15 each to hear the rock group do their thing.
2. To follow one's bent; for example, to be engaged in left-wing politics, some sort of meditation, or use of drugs (particularly in the sixties).
The hippies were doing their own thing when the cops came and busted them.
3. To be engaged in an unusual activity that strikes others as odd.
Leave Jim alone, he's just doing his own thing when he's standing on his head.