I think it's really cool that you're asking about this. Frankly, you will never fully understand unless it's something you've experienced yourself. But that doesn't mean you can't try to understand, especially if you have a friend who does struggle with self harm.

I only recently started cutting as a habit almost a year ago. Before that it was literally once in a blue moon. But the reason why it was a habit in the first place was because I'd think back to the times that I did try it, and how much better I felt. Cutting is different for everyone, but I'll explain what it is for me.

1. Relief. All the emotions and feelings that I can't name or explain are released. I literally feel something exit me. It's like wearing a tight pair of roller blades all day long, getting home, and removing them. This release actually releases endorphins that the brain interprets as "good", so you go back for more. That's where the addiction begins.

2. Punishment. Sometimes I truly believe I deserve it. It's treating myself the way I feel I'm deserved. I feel worthless, invaluable, therefore I should hurt myself.

3. A reason. Many times I'm just sad. Or angry. And there's absolutely nothing I can pinpoint for these emotions. I get angry with myself because there's nothing to be upset about. Well cutting is pain, that's a reason. I feel distress, therefore I'm given a reason to be distressed.

4. To feel. Sometimes I'm just numb. There's nothing. I feel absolutely empty. Cutting makes me feel something.

5. Just because. This is the hardest for non-self harmers to understand. Cutting really is an addiction. There would be days I'd cut for the hell of it. Not because of any of the above reasons, but because I wanted to. Because it felt right. Because I felt like I had to. Coincidentally, feeling like I have to leads me to distress which gets me to reason #1.

I hope this helps. This list is by no means exhaustive, but it should offer some insight. But please do not take this as a suggestion. Although you have those bad thoughts, you do not want to engage in this. If you start, you will not stop and that is a promise.