Hard to look at him without seeing how he betrayed me

One day my husband left his laptop open and I looked through his emails and discovered a whats app backup of messages between him and a colleague. When I confronted him, at first he asked why I was going through his emails. He saw the anger in me and quickly changed the story to they were just text messages. After I booked a therapy session he was really quietly angry and at the session he revealed that it was a full blown affair. When I cried he didn't even come and hold me. I went through such hell in the next few weeks. I couldn't even get out of bed. 20 years of my sacrifices down the drain. To make matters worse the colleague was young and beautiful. My self esteem was at an all time low. Since Ethan we have been trying to salvage our marriage but I find it hard to look at him without seeing how he betrayed me. What can I do to overcome this hate I have for him?