I know how you feel!! Unfortunately- we all do!!:(
When I first found out my wh was a liar and a cheat- I actually expected that I'd die of sadness and despair!! I was an absolute zombie and I also had no idea how I'd deal with the mind numbing devastation which follows!! I lived from minute to minute- in the shocking revelation that the person who I had trusted for over 32 years could have done this to me!! And I had absolutely no one to talk to!!
I'm so very sorry!! What happened is not your fault!!!!!They're weak and damaged!! I too- was worried that I'd screw it up- and then I had the realization that it was him- who should be squirming!! I know it's extremely hard- but you have to stay strong!! And my no means- do you back down or appear weak in front of him!!!! Let him worry- about what you're doing!!!!!
My heart goes out to you!! Post often- seek counseling- or if you're lucky enough to have a trusting friend- talking does wonders!!