People self-harm for different reasons. Sometimes it's a release from a pain that can't be expressed in words. Sometimes it's a distraction for the mind from having to deal with said pain. But whatever the reason, they are not pity scars, nor are they an attention seeking behaviour. They are the physical manifestation of a tortured soul.
It doesn't help to be condescending in the way you talk to or the way you approach the person. This person is hurting. Beyond your understanding.
DBT skills have helped me a lot in dealing with this over the years. Self-soothing is an important skill in learning to deal with self-harming urges. It is the opposite of what you instinctively want to do, but that self care and love is what you need at that critical point.
Sometimes it helps to talk to someone when you have these urges. Unfortunately, it is still a somewhat unspeakable act, and taboo in social circles. But if you can put into words how you are feeling, sometimes that is enough.
If that is not enough, you need to try other techniques. These might include getting ice cubes and holding them against your closed eyelids. The shock of the cold sometimes gives the same release that self-harm might. Another thing to try might be drawing on yourself, or flicking a rubber band against your wrist. If need be, PRN medication is an option. Anything to get you through the next 5 minutes without self-harming. And once you get through that 5 minutes, start over again. Postponing it gives you a chance to deal with the emotions. Say to yourself, "If I still want to self-harm in an hour, then I can do it." And hopefully by the end of that hour, you will have dealt with the emotions in a healthier manner, and you can be proud that you made it through one more time!
So next time you feel like self-harming, remember that you are not alone, and it is not the only solution.