I'm sorry you are having a down day, and I'm sorry for the others here, too, who are suffering. Just know that everything you are feeling is completely normal. No matter how much you work on your detachment - and you have done an EXCELLENT job on this - there are still going to be things that he says and does that will hurt, and I'm sorry for that.
Remember to give yourself a break. If you need to cry, then cry. If you need to yell and scream about what a no good SOB he is and what a heartless demon that sorry ow is, do so to us here. We will validate everything you are feeling. I also have a very dear friend who allowed me to let it all out to her when I needed to. I never had to worry about her judging me or telling others. She would just listen and validate. And when my husband and I reconciled, she supported my decision and renewed her friendship with him. THAT is a true friend, and we all need someone like that in our lives. If you don't have a friend like that, can you go talk to a therapist? That is another "safe" place where you can let it all out when you need to.
Keeping the pain and hurt all bottled up isn't physically or emotionally healthy for you. Allow yourself the cry and rant, and then pick yourself up and dust yourself off. There were days when it would take all I had to get the kids to school, and I would come back home and literally pull the covers over my head and sob. But then, I'd get back up, take a shower and get on with life.
I admire your strength and grace throughout this battle for your marriage. You are an excellent example to your children, and I promise you that they will look back on this time later in life and appreciate the fortress you were for them. Only YOU know when you are done fighting for your marriage, and if/when that time comes, I will support your decision no matter what. Just keep taking things one day at a time, sometimes one moment at a time. Know that we all here care about you!
Take a hot bubble bath...eat some chocolate...drink a glass of wine...get some rest!