I read this a long, long time ago (I guess maybe 15 years ago, but the book was definitely older than that, I would guess at least 30 years old by now, probably older) and am not sure if I got the details right. Also, the story might have been of German origin. I think it goes something like this:
A young man receives the ability to stop time around him exactly once, i.e. to live in that moment forever. (It might be a magic watch that grants him this power) He continues to live his life, always looking for the right moment (the right moment for him is the one of true happiness), but can never choose the right one. I think bad stuff keeps happening to him, preventing him from being totally happy. At last, he is a very old man and I think the ending is that he lies down next to train tracks, stares up at the night sky/stars, and feels truly happy having lived a long life and experiencing this peace at the end.
Does anyone know a story like this?