Keep going - at a certain point of learning to detach, you might be able to take your anger out and look at it....it's usually there because we are not getting what we want and/or we are hurt beyond measure...understandable for sure...and also a function of our needs...which are also okay.
The thing that is so tough to get to and takes time for most of us is that we have to realize our S is on their own life journey, and they do have that right, no matter the consequences to us and/or kids. Not easy...in fact brutal to get to this point.
Once we get there you can look at your S for what they have gone back to...being an individual...not part of a M...or maybe still part of it but not consciously known to them anymore.
If you can see that troubled soul for what they are...then the anger starts to diminish. And if an affair? That's the worst anger to have and also very understandable. It takes the most effort of your life to accept, and actually you never accept it. You just recognize that your S ended up there, and probably not with that intention. You learn to be yourself again in a new world with a new future that may or may not include your S depending on the sitch. The anger gets compartmentalized maybe, and doesn't consume you as much. This may be an issue you have inherited in your life for good, how could it ever not be a part of you if the one you love(d) cheats? Time does heal and provide its own wisdom.
