Please how do I get over this bitterness?

I had a boyfriend EXACTLY like this. I thought he was Mr. Perfect and that nothing could go wrong. He always told me how he really saw us getting married.... this was until I saw him texting an old girlfriend. I was so upset because I had been on vacation for about a week with my family and before we left everything seemed ok. He had been on vacation before that and got high causing us to fight some but I didn't react like I should have. I should have ending things right then but instead we stayed together. When I asked him about talking to her, he immediately lied and tried to turn it around to make me the bad guy before he finally admitted that they "hung out" while I was gone. She has a reputation for being very promiscuous and is a drug addict so she clearly would have no problem with the poor choices he made. I still have feelings for him but every time I start to miss him I just remember the awful things he did and that now she (and the other girls he is dating at the same time) have to deal with the problems he brings. Be happy that you are no longer with someone like that even though you may still care for him. I ended up deleting my ex on facebook and blocking him so I could not be tempted to see him. Also, I deleted his number. It's so hard to make decisions like that but in the end it's best for you and you have to keep YOUR best interests first.