What I've learned from Doctor Who (2005-present) about relationships...
You want to be Rose or Oswyn, not Martha, and when you realize he'll never reciprocate those feelings, you take on the role of Donna or Amy. Or you do like Martha, and abandon ship. River Song... that's a whole other story, dying when he first meets you, and when you first meet him, you try to kill him... very complicated.
In all honesty, I've never been Rose to any guy, if I was, it would be complete news to me... like that one time I found out I had a boyfriend in college... yet I didn't find out until three years later... felt kind a jipped, not even MySpace official!
Always the Martha, usually, I do end up acting like a Donna or Amy. At some point, I learn to throw any feelings I had aside and accept it as is. Become just the friend. Usually the quickest way for that to happen is the introduction of a girlfriend. Or worst case scenario, I discover I was completely in awe of the idea of who I thought the guy was, rose colored glasses are ripped off, and I discover this whole time... he was a toad. Which in that case, I question what I thought was so wonderful about this toad.
I prefer my sugar-coated spacey idea of love. Which is when you really love and really care about someone, you would travel to the edge of the Universe for that person... like they would for you. Not just a measly 500 or 1,000 miles (you probably know which songs I'm referring to).
The harsh truth is, if the guy wants to be present in your life, he will, and he will travel to the edge of the universe for you, he'll be like Rory Williams, or a Mad Man in a Blue Box.