James pov
James always pranked people with Sirius. Not because he wanted to. No. It was because he felt bad for him. Sirius had terrible homelife with abusive parents and a brother who didn't even want to look at him anymore. He wasn't allowed to talk to one of his cousins, one of them went insane and one of them always followed her parents. The least James could do was do anything Sirius wanted.
Only once James said no. And that was because Sirius wanted to prank Peter and Marlene. James' childhood best friends. James knew how sensitive the two of them really were so he tried to tell Sirius not to prank them, but of course he did.
So when James found out that Sirius burnt copies of their belongings, keeping the actual ones safe, he was furious. But he knew he couldn't lash it out on Sirius, so instead he bottled it up inside of him, like always.
James couldn't sleep that day, he couldn't eat, he couldn't do anything other than stare at the ceiling in his bed.
You could've stopped Sirius, his brain tells him but James tries to shut it off.
Peter and Marlene wouldn't be crying in their beds if you stopped him, it carries on.
You're worthless, it finally says before James sinks into those thoughts, silently crying until he falls asleep.
The next day James got a letter at breakfast. He was confused as he never got letters since his parents died, last year. When he read it, it all made sense.
To Potter,
We can't be friends with you after what you did to us. From now on, we don't want to talk to you, we don't even want to see you.
Peter and Marlene
He knew how sensitive the two of them really were, but they didn't know how sensitive he was. They didn't know how easily bruised his ego can get. So he left the Great Hall, when he felt the tears start prickling in his eyes.
He entered into the dorm bathroom and got his razors. He cut his forearm line by line until it was all covered in red and you couldn't actually see skin.
Then suddenly, he heard "JAMES!!!" but he couldn't register anything else.
He started seeing black spots and felt a large bang on his head before everything stopped...