It's more than just knowing the chance isn't there though, it also means finding a happy place with that. Being attracted to someone doesn't mean you can't be there for them, or that you can't fully be just a friend.
Life is messy. People do their own things, and they mesh or don't mesh in whatever way the circumstances allow them to. This guy's doing his thing, and you're doing your thing, you just happen to have a few extra butterflies flying around. And you can't act on it, oh well. It is what it is. It's life. It's sort of paradox. Accept the messiness/complications, and it becomes extremely simple and straightforward.