Why I loved "500 Days of Summer", when it seems like no one else did

I went to see 500 Days of Summer at the cinema, and I loved it. A lot of people I knew hated it, not helped by the line early on that states that there are two kinds of people in this world: men and women. I think that is a stupid thing to say, even in a romantic comedy. And it's not even correct in the context of their story. So I just ignored it and enjoyed the rest of the film.

I then went to see it for a second time, leaving work early one day to bike over to the cinema for a late afternoon showing, and I liked it even more. I have now bought myself a copy on DVD, which I am watching right now.

I had crushes on both the male and female leads for the duration, and I loved the scenes where they were play acting in the ikea show homes, the karaoke, and the bit in the park where everyone suddenly starts up with a synchronised dance routine was amazingly cute but the thing that got me, and made me want to watch the film again and again was my total over-identification with Tom, the one who falls in love, with Summer, the one who doesn't .

The story:
Tom starts seeing Summer, who he likes. Who he really likes. To be fair to her, she states early on (whilst in the ikea show home) that she's not really looking for anything serious, and he hears that. But things develop, and they get closer, and he falls in love even though she doesn't even believe in love. He knows they're not boyfriend/girlfriend, but he let's himself get carried away, interpreting her actions in the way he wants to, even when she is saying something else. Things carry on, with Tom suspending disbelief, until Summer tells him she doesn't want to do this anymore and he falls apart.

After putting myself in Tom's position so many times in the past, I can safely say that for me there are few things more dangerous than becoming emotionally invested in someone who wants different things to what I want. This is why the film struck such a chord with me.
I am terrified of that situation (and each time it happens I feel stupider for falling for it again), when you have something with someone which seems so much like what you want it to be that you pretend to yourself that it is that thing, the Relationship with the capital R . It seems so much like one, and you want it to be one so badly, that you ignore the reality that contradicts your expectations. You even allow yourself to be heartbroken when the other person shatters it. But ultimately, the thing that I've realised is that, if my heart breaks in this situation I have to take responsibility for my part in it.

I would like to say it will never happen again, but I think I said that the first and second times it happened. But at least I have gotten better at realising when it's happening and I can happily report that it's not happening now.