1. Reasons with some acquaintance with logic
a. Because it is scary to think that mankind is without help or guidance, and is running amok overpopulating the earth and wrecking the environment. And if this is indeed the case, it won't be helped by me worrying about it.
b. I prefer to believe that there is some kind of life after this one. And if I'm wrong, I will have lived at least as happily believing, and no-one will be able to say "told you so" afterwards.
2. Real but unlogical reason
I have resisted Christian friends who tried to "save" me; it makes no sense that a little clique would be saved and all outsiders damned; this stuff tends to make me want to side with the outsiders. But the essential Christian message - love God and your neighbour as yourself - simply feels right to me, a sort of release of tension and satisfaction, like solving a mathematical equation.
So, in my case, I'm not sure that faith sustains the belief. But living optimistically in faith feels good anyway.
™ Version 4.2