At some point in our relationship, I noticed she had developed a new smile, my smile. I used to see it in her face every time she looked at me, when I made her laugh, when she woke up and saw me watching her, after every single kiss. That smile was reserved especially for me.
After we broke up I realized I missed her when I stopped seeing that smile, my smile. Even when we coincidentally ran into each other on the street, the market, etc. She never smiled at me like that again.
After we broke up I realized I had fucked up badly when I saw her once, with a guy, at the park, giving him my smile.