Most Helpful Guy
Because you were attached to him at one time. After you fall in love with someone you still care about them even though you don't want to be with them anymore. It's normal and just takes time to get over him.
It's like losing someone dear to you, it's very hard at first but over time you learn how to cope with it. But still thinking about it even after a long time will still make you sad because of the memories you have shared and the fact that you love or once loved them.