I Lost the Girl I intended to Keep

I started talking to a girl online. At first, I thought nothing than just friends, we started talking day and night constantly, we made each other smile so, we decide to meet each other until one day I realize that I fell for her. We met again and again and we became bestfriends and suddenly we were in a relationship.
Months went by we were strong until years passed arguments came. We always go through every problems we have, whenever one of us messed up we always forgave each other but this time I thought I started loosing feelings and she starting to feel unwanted so, she broke up on me eventhough it's really hard for her. She didn't know what to do, she cried most nights.
Months went by, I started to think that I miss her, that I still love her but I found out that somebody who made her happy.
She's gone! and now, I'm the one crying at night knowing that she belongs to somebody else and all that's left are memories.
I lost the girl I intended to keep.