It might suck but it's just something you have to deal with, and it almost certainly won't be the last time this happens in your life. It's been in my experience that you always kind of feel something to some extent for the ones you love. Not necessarily love, but there's always something there for that person. However I'm sure this changes over even longer periods of time, I'm only 21 so I haven't had 10 years since a past love to know for sure.
I left this past GXL early for a girl I was really into that wanted to go to the bars that night. After that night we were essentially inseparable for the next three months or so. I fell completely head over heels for her (yes, in love), more so than I had with anyone else up to this point in my life in such a short amount of time. Although no one is perfect, she felt perfect for me. Without getting into details, she basically used me to get over an ex-boyfriend and had been lying to me during this whole endeavor. While she did have legitimate feelings for me, her long term goals weren't the same as mine, and we weren't on the same page as far as how much we liked each other. Even though she did me wrong, I wouldn't say I regret it happening. I learned a lot from the whole ordeal, about myself and what I'm looking for in future relationships.
Basically, don't dwell on it for too long. Have your brief period of sulk and get back out there. Some days will be better than others, and she'll still cross your mind, but you just have to keep chugging along. Be sure to resist any urge to talk to her, because it will only revert any progress you made if you do speak with her. To throw the cliche terms out there, there's always more fish in the sea, and it's better to have loved and lost than to have never loved at all. Take it as a learning experience, get back out there and find someone new. As I said before, this most likely won't be the last time this happens in your life.