I've had a long history with this. Actually, I still do pick my skin..not nearly as badly as I did when I was depressed and without medication though. I have a bunch of white-pink marks on my right arm from all the picking I did. I stopped beating myself up about how it looks now, by thinking that actually the marks kind of look like cherry blossoms. Like when they have a Sakura blossom pattern on a kimono, so it's actually sort of pretty in a odd way.
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"Sprinkle, sprinkle, little bar, what I wonder is a cat" - Cheese from Foster's Home for Imaginary Friends