Ahm, I think the only person who knows how to make your friend happy again from the inside is your friend himself.
But let me share some--maybe similar-- experience I had...
That ever happened to me, when I tried to cover the pains and hurts, I'd be charming, outgoing and such, but it wouldn't last too long, I would always want to come back to my room where I could detach myself from the outside bad forces.
The thing to work that out was to find another new extremely interesting thing. I packed everything I needed to travel somewhere nobody knew who I was, just for a while. I began to have new things to learn and understand, and to explore what others didn't really notice, I didn't do it all during the traveling, few earlier new things at the vacation, the rest was when I came back. I didn't put any focus on the problems I had had before. Learn learn explore explore, then eventually it gained me new understanding toward the previous problem I had ( earlier, people would tell me to see bad things from bigger perspective, but I couldn't do with only knowing it, I needed the feel to understand the reason and the outcome of looking from better point of view).
After finally I felt good to see those things in better way (made up my mind), I could easily cope with the problems pretty well.
Anybody doesn't have to travel to Fiji just to handle the unhappy feelings, but I came to conclusion that possibly people like me need the mind leverage to deal with stresses, they way would most likely to learn new things.
You know, and we all know that the mind and the realization of what's on it is unstoppable, but still things can change when the focus alters.
On a daily basis we deal with people shooting us down, ridiculing our ideas, telling us they won't work etc. Do the opposite for him. Be that person he can talk to that about anything, that will provide him encouragement.
I have recently found myself a confidante of an ENTP who seems to be often unhappy. Not in a suicidal way or anything, but enough to worry me and I don't know what to do. Some of this seems to be from the problems he has with his girlfriend, who he loves but they also argue a lot. Some of this seems to be from general dissatisfaction with his life.
He puts on a happy front but often tells me his true feelings.
Anyways, he says I can't really help him and when I try to get him to be positive he doesn't cooperate very much, sayings hes sick of trying to be happy and that nothing can help him. What should I do about this?
Get your friend out and find him something to do, something new to be interested.
Encourage his Ne. On a daily basis we deal with people shooting us down, ridiculing our ideas, telling us they won't work etc. Do the opposite for him. Be that person he can talk to that about anything, that will provide him encouragement.
Don't take this the wrong way, but have you ever considered that he doesn't want to leave his girlfriend for you?