I have recently started a really bad habit of rubbing my scalp with the ends of my fingers when I am sitting on a chair. I rest my elbow on the desk and use my hand to support my head (as many people do) but before I know it I'm rubbing my scalp and picking out bits of dandruff. I really want to stop doing this because I'm sure it's damaging my hair. On top of this it looks as though I have headlice, which I don't (though I did and I think I started this habit because I was paranoid about them returning) and by the time I've finished my hair looks like a nest! Please help!

Maybe if you got rid of the dandruff you would be able to break the habit. And maybe wear your hair back in a ponytail or something so it's harder to mess up.
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Each time you notice your hand on your head try to think of something else. Try rubbing your temples instead. You'll get a small "reward" from it. (: