My partner had an affair and I can’t forgive him

We were planning the next stage in our lives together when he was seeing another woman. He wants us to get back together, but my heart has turned to stoneMy partner of five years recently had a short affair with another woman. It came when we were very happy together and planning a new phase in our lives. I found it devastating. I moved out and ended our relationship when I discovered it. He wants to reconcile. He says he is frightened of happiness and that it was a deliberately destructive