You Just Don't Know It

I think this is about a boy liking a really good friend but he doesn't want to show it for fear that things will change between them.

The boy doesn't understand how the girl can't see how he feels about her.

There's too much at stake (their friendship and/or relationship) so for now, he'll "stay alone" and deal with it.

Basically, the girl is oblivious to the fact that this boy is in love with her!