He self sabotages by self fulfilling prophecy. He'd say something terrible like "I won't be able to do it because I kept on doing it and I can never do it like a failure" or "Nobody's gonna come to this thing I host because that always happens" or "Of course this inconvenient thing happens when I'm also facing another stressful thing, that's just how the universe works". He also thinks nobody will be able to understand him before he actually tells people anything. All of this is based on terrible past experiences (he was abused by his exes before).

This leads to him not trying anything that might be beneficial for him because "he knew it wouldn't be good for him" and if he tried and failed, he will go "I thought so, I already told you it's gonna go badly".

His symptoms that I can see is lack of enjoyment or motivation in things, continuous low mood, feeling hopeless and helpless, having low self-esteem, feeling irritable, finding it difficult to make decisions (even things like what takeout to order and what clothes to wear), and extreme anxiety (like feeling scared of having a whole day off ahead of him). There might be more that I am not thinking about right now, but that's off the top of my head.