It means “Stop being fake”
Look in the mirror, and start loving the real you.
The fact that “and it shows”, means that the person targeted is probably constantly complaining about their physical appearance, or, they know they’re doing stuff that’s wrong, they do it any way, and then they complain that they should have known better after the fact.
You are struggling and getting no where. All the struggling is showing with no improvement. It is a kind of insult.
It means you have been insulted beyond all toleration. If somebody has said this to you it’s a piece of verbal aggression that equals a punch in the balls.
That you’re constantly trying to change yourself for the better and it’s evident that you’re struggling in trying to achieve that.