Can’t let go of my exs opinion of me

For years we were together and he loved me and cared and so I had value. I was happy. Now he ended it moved on and wants nothing to do with me- and almost a year later , this entire year it’s been over, I have felt and still feel like I’m nothing bc he doesn’t want me. I just wish I could get over it. If I was valuable he’d still be with me.