People say it is a method by which some deal with unpleasant emotions, do you think that is the case for you?

Methinks it could be hereditary as well. My father rubs his knuckles quite a bit. That may not seem as severe as scratching your face until it bleeds, but after rubbing for so many years his knuckles are but bruised calluses. He says it soothes him. I personally engage in this behavior because the thought of something being in my skin aggravates me.
What I'm getting at, is there are a lot of different reasons behind it and figuring out what drives your picking habit could be very helpful in breaking it.