I think it is due to the attachment and unfulfilled expectations. Everyone deserves to be loved and to be happy. But it really pains if you love someone so truly from the bottom of your heart and it goes unrequited. You will never completely move on if you ever truly loved her, but you will have to start living with it. Memories don't hurt. Love doesn't hurt. It is the attachment that hurts. It is the expectation that hurts. It is the imagined future that is now broken that hurts. When we lose someone that we love so truly and they walk out of your life for some reason, it hurts. This doesn't mean memories will haunt us. It is the collapsed future that hurts us. Living in the past with the ones we love brings us tears, not because that is lost, but because there was something that could have been forever, but it isn't now. That hurts. That stings and we tend to associate it with good memories. Sometimes we love people more than the memories they gave us. We fall for the
You think you are immature because you remain single while your ex had so many men after the break up? This is not immaturity. May be she just prefers casual feelings to get relationships where as you prefer one girl to many girls. Just two very different perspectives but not immaturity. Yes introverts are slow in adjusting to the changes around them unlike any average person but that is how we are.