I have a question about a phrase (an idiom), which can be roughly said as:
You have only one life (to live) and it's not going to happen again.
I'm not sure if it's correct, most likely not. What I want is a meaning of this phrase, not said like "You have only one" but like "Life is just one" or "One has only one" if you know what I mean. Not saying to someone: "You have" but saying it like a general statement ("One have" or "There's a..."). Something like:
One has only one life and it's not going to happen again (or repeat).
I thought about replacing the part "happen again" with something like "repeat" which would suit better from my point of view but as far as I searched the web, it's not used in this kind of phrase.
Suggestions for more less widely used or known phrases welcomed.

