I miss mine too even with all that I know and the different cheating over the years. I have 2 kids and a job that keep me busy most days but when I'm by myself it's when I miss and hate him the most. The people around me just say I miss the company of someone being here, not so much my husband. Everyone says we lived we separated lives anyway and we were more like roommates even though I didn't see it like that. I unfortunately have to be some kind of friends for my kids sake but I don't like ex's being friends either. Feeling sorry for your ex is so normal since you spent so long together it's natural but you are not responsible for him. Just like anyone else you feel sorry for they are responsible for themselves and you need to keep going and don't let them take you down with them.
The advice I keep getting is to just keep moving forward and everyday the memory will fade farther and farther away until he is just an after thought. There is no secret formula and that we just have to keep going and be happy with ourselves and with what we have. And try and surround yourself with goodness and happiness.
If I something else that works I will let you know. Stay strong you did and are doing what is right for you. I hope this helps.