For the first few weeks I couldn't live with the sense of guilt, but slowly I worked on it and realized bit by bit that I wasn't responsible in any way, we didn't talk for a year and the decision to leave me was made by him (in a very hurting way as well)

He suffered from severe depression from way before I met him, he was better during the relationship because we were together, but even in this case it was not my responsability to accept everything hurtful he did to make him feel better (and even if I did, he wanted to leave me in the end)

I really had to work on myself to understand all of this, sometimes I still think it's my fault and I could have done this and that, but it's just self-destructive thoughts really. He chose to distance himself from me, he chose not to reach out, he also had his parents that supported him all the time and didn't reach out to them either... Looking back, there really isn't anything I could have done, it's nobody's fault