I had a self-harm period in high school, since with social anxiety, I couldn't cope with depression with drugs (requires knowing people), sex (requires knowing people), drinking (requires knowing people), so... with scissors in my room, it just naturally followed suit. Didn't help when I was in such a dark period of my life where I thought I deserved to bleed, too.
It was such a downward spiral. It gave me anhedonia and I just felt worse and worse each day doing that, and eventually had to do that to feel "normal", all while doing what I could to hide it from my classmates. In the psych ward I had to stop cutting, and succeeded then, but even today I still entertain the idea of wanting to cut myself... before realizing where that would just leave me; even lower than before.
So I understand self-harm. It's a really sad thing to experience.