I shouldn't feel like this

So I accidentally reactivated one of my Facebook accounts and I didn't have my ex-husband blocked on it. So I decided to scroll through everything on my news feed and I saw picture of him and his new girlfriend the one he cheated on me with kissing and I just have this feeling of wanting to cry. And I really don't know why because for the past six months I have been doing great I have accomplished so much and I haven't cried about him cheating on me and leaving me for her in a long time but that picture just made all of my feelings come back. It made me realize how much I dislike him.... but it also makes me happy to see him happy. I hope one day I can find my happiness