Stay or Leave?

Yesterday I received a broadcast through my blackberry that attracted my attention to it, I don't usually read broadcasts that are about love and poetry but this one really got me thinking, the broadcast was a simple question, If you loved someone and you realize that you can't have him, would you love him to the end or would you leave him? I have sent the broadcast to some people in my list to see what does people think about it, I only received one answer because apparently lots of people simply don't read their broadcasts if the seem to be poetry or something related to love.
The only answer I received was to let go and move on with life. I believe that its a hard question to answer so what I'm going to do is explain some theories and at the end I will try to answer it.
I once read somewhere that the human nature is designed to be able to love who it hated once, but unable to hate who it loved, love can replace hate while hate can't replace love, when we really love someone it's really hard to move on and forget this person, we might forget the person for a while but deep inside this person is still around. In some cases it's worth it to move on and forget some people who hurt us or done something that really affected our life in a bad way, moving on without these people is a must to live a better life, but what about people who didn't really hurt us, should we just forget them just because we couldn't have them in our lives? what happened to unconditional love? Do we always have to wait for a return for everything we do?
I remember watching the movie TITANIC when Rose loved Jack even though they were impossible to be, her family was rich and she was engaged already to a wealthy guy, he was poor and can offer her nothing but love, it would look impossible for them to be together but that didn't stop them from loving each others. there are tons of other examples like this  that shows that we don't need a return for our love towards someone.
But what if this love is hurting us and not allowing us to live happy, what if we are living on a hope that someday we will be with the person we love, and by that we stop every opportunity we have, every future we can have, and every person who is interested in building a life with us, it would be like waiting for something that will never come, or waiting for a person who we know for fact is dead. In this case I believe that moving on would be the best solution, I know that moving on and trying to forget seems impossible sometimes but that's life, its hard and it's cruel, we will find it difficult at the beginning but its better for us.
You see the different cases and different scenarios, these are some few things you have to think about before answering the question, should we stay or should we leave? In my case I always go for the first option, I would stay, I believe in unconditional love, I don't expect people to love me back, but I try to love people and create a better relationship with them, it's not really easy but it's the way I look at things and I see it as the right thing to do.

Cheers :)