its in reference to a montaigne quote, "parce que c'etait lui, parce que c'etait moi" then how would you say in french, then, that because it is us, that life will never be the same? i know, i know, why write a love note in french when it isn't my native language? :)
How about: Parce que c'est toi, parce que c'est moi, parce que c'est nous, la vie devient un magnifique et constant rendez-vous"
You've awaken the poetic streak in me! lol It doesn't translate as what you wanted, really, but it's pretty (I think) ! :-) Wait for other suggestions though, I'm sure you'll get plenty more, and better ones too!