The skin picking or hair pulling typically involves some sort of self soothing. It reduces mental stress and anxiety.
An irregularity in a hair or skin surface is picked off, often played with or eaten, which produces a feeling of something being put right or an imperfection removed, and a mental release follows.
It's extremely difficult to stop on your own for an extended period of time. Some patients can overcome the specific behavior, but it reappears in other areas, like picking in another body location, or just anything similar really.
Look at the situation you are in when the behavior occurs. Where are you or what are you doing? Alone on a Saturday night, in traffic, whatever. Therein lies a clue to where the anxiety or unease is coming from that needs to be soothed by picking. Write a picking journal with times and locations. You will eventually see a pattern.
From there you just keep looking deeper into what's making you need to feel soothed in that situation. Do you feel not competent enough or imperfect in crowds, on a date, while driving? What are you reading about or watching on TV while you pick? Does it remind you of your childhood, problems with family growing up? Your mother, or father? 🤷🏻♂️
Then you start taking other actions or mastering skills that make you feel Ok in those situations, and the need to pick should weaken.