I TOTALLY understand where you are coming from and I felt that way initially when I separated and began divorce proceedings. I was mad as h3ll that my XH cheated on me then moved right on to be with her and ultimately even married her. But, you know what I learned? She is NOT living my life. She is living her life. Granted, my XH and I don't share children, so I may feel differently if we did, but he did have children from his first marriage when he and I married and I have actually urged his daughters to have a relationship with her because she is their stepmom now.
I have been where you are, honestly. I don't know if this helps you or if you even want to hear it, but the thing that worked wonders for me was a good counselor. I didn't date for awhile after my D because I just didn't feel like I was in a place to. I think that is a decision everyone has to make for themselves, but for me, not dating helped me focus on my own life and let go of "what might have been" if my XH had kept it in his pants.
I agree with what Juju said about how he'll continue to cheat on women. I honestly believe once a cheater always a cheater because it rings true over and over and over and over again with most people who cheat. The best thing you can do is focus on yourself and just continue to provide a strong and stable role model for your kids. They will see the truth and probably realize even more than you know what is really going on.
Hang in there!
Me 52, H53 Bomb drop 9/29/2014 Divorce from XH final 12/17/2014 Marriage #2 12/31/2019 5 adult (step)daughters (3 from XH's first marriage, 2 from current H's previous relationships) 6 grandkids