Any action or behaviour that you feel is not useful, compulsive (or it could say "but you do it anyway"), and is causing harm to yourself.  This can include nail biting, skin picking, hair pulling, overeating, overspending, over-working and other things.  It can feel as if you have little to no control over whether you engage in the behaviour, or it can occur without even realizing it is happening.  Unwanted habits can lead to guilt, shame, low mood, and anxiety, among other things.