You ask a really good question: “What can bring a man back from the very edge of despair — back to a life of usefulness and focus?”
Love of God or your fellow man can do that. A friend of mine was a farmer, foreclosed on by the Bank after a long drought had made it impossible to pay the mortgage. His wife had already left him, and had taken the kids with her. The farm had been in his family for four generations, and on top of everything else he felt that he had let his family down by losing it. A friend came to see if he was OK, and found him in the barn, in the act of throwing a hangman’s noose over a beam. He talked him into coming into town and going to see a counsellor used to dealing with suicidal farmers: there had been lots of them during the drought.
The counsellor told the farmer: “I understand your despair: the only thing that can save you now is to find someone worse off than you and try to help them.”
The farmer lifted his head and looked the counsellor in the eyes:
“How can I find someone worse off than me? I’m 60 years old, have been a farmer all my life, I know nothing else, and now I’ve lost the farm!”
“If you go looking, you will find them.” The counsellor replied.
The farmer was so angry that he set out to prove the counsellor wrong and found plenty of people who were just as endangered as he had been, people who still had their families with them, still owned their farms but saw that it was inevitable that they would lose them, and thought they were on their own, that no-one cared. Perhaps he never found anyone who was actually worse off than he was, but he found a reason to go on with life.
He founded Farm Aid, a charity that gathers groceries, stock feed and toys for children and delivers them to farms in the worst hit areas. The psychological benefit from the farmers knowing that people in the cities cared enough to donate food parcels for them was immeasurable. The Farm Aid CEO told me “I knew exactly what these people were going through, and I got so busy trying to help them that I forgot about my own situation.”
So the answer is Love: when life seems to have nothing to offer, find someone worse off than you and try to help them. My suicidal friend is happy with life now: he knows that what he does helps others, and his life has purpose.
Happiness is not something to be sought directly, it is a byproduct of being useful, loving others and being loved in return