Remember he isn't an extrovert. Nonetheless I would take Tikka's suggestion with the phrase "some social events" even if he feels crappy at least get him to hang out with friends, and after he feels better, some strangers.
People do make mistakes (for him, the Nice Guy Syndrome), but he should have seen this coming. Perhaps he did, which makes it all the worse for him.
Love wouldn't exist without loneliness to inspire it.
Peach yogurt is made of love. And gnome kidneys. - Domino
I can cope and will cope without polluting my lungs. - Saslou
Not this thing again. No, of course, do not tell him to do THIS! Leave that to the movies.
As to the OP. You know what, other than listening and talking to him and trying to get his mind off of it, there isn't much you can do.
However, as he has a history of taking things too far, as you suggested by the suicide attempt, you shouldn't just let things stay as they are. Talking to him about it is the best way to go. I know INFJ's have the tendency to just block everybody out even if they want help, so you shouldn't let that discourage you. It can be very frustrating but if things get bad, it might be best to push it a bit further and not let him sink into withdrawal mode. Try to make him face the cold, hard facts. Talk, talk and talk some more, even if it is difficult for the both of you. It might shake him up and make him to start thinking about things more clearly.
What Tikka suggested about dragging him to go out can also be helpful along with talking. The idea is to get him out of his comfort zone.
If you see that things are getting really bad even if you have tried talking to him about it extensively, you might think about suggesting some professional help to him. Talking to someone who is not involved in it personally can be very helpful.
Yeah he does want change, he just can't stop thinking about the issue. Hell the other night, he suddenly wakes up and says "they moved in together..." and freaked out for a bit.
You guys are sleeping in the same bed?
But yeah, I can relate to him. The thing is, his condition is amplified when he's alone or alonish with you. That's the crux. He will only be able to set his mind somewhere else when other people (preferably nice girls) are around him, so he sees more opportunity (for the future) instead of looking back in his head.