I've made myself sad by re-reading the orange_crushed fic I just recced.
The first time I read it, the mistaken escort/pickup situation is what stuck with me the most.
This time, it's the part towards the end where LZ reflects on how incredibly lucky and unlikely that mistake was, how sad he was before meeting WY, how horrible it is to imagine a version of himself in a timeline where they never met.
They love each other so much, they each make such a difference to each other's lives.