Let's say that you currently look like Edward Furlong in Detroit Rock City -- 21, kind of a slacker/stoner, a little heavier than average (but taller than he is by a few inches).
Then you clean up, but keep the shaggy hair, lose a bit of weight, but your face is still long with those high cheekbones and you look more yourself, like you did when you were a kid in Terminator but now you're 23 years old.