(Have been lurking since the beginning)
I think Blood means that it's too late, because the affair has already happened and therefore, your marriage will never be the same, even if you do stay together. (Correct me if I'm wrong, please, Blood).
This doesn't mean it won't work, just that it will be a different relationship than the one you had before; different can mean better though. It does for me.
I think to really face up to it, and to 'stop pretending' that all is ok, you have to talk to someone in RL. I can't tell you the sense of relief I felt telling people what was going on. I told colleagues firstly, (now friends, not just colleagues), as I almost collapsed from the stress of it all in work the first day back in work post D-Day. I told a couple of close friends. I really didn't want to tell my family. I thought my parents wouldn't understand, would blame me, or maybe it would worry them to death. I couldn't have been more wrong. Their support, warmth, love, care and understanding was like having a safety net below me when I was on a high wire. I could let go of all the fear, in the knowledge that, should DH and I not be able to reconcile, my parents would be there to help out if I needed them to.
Telling them and my friends, made the affair real. It made me realise that I had friends who valued me. It made me realise that while DH was telling me I hadn't made him happy for a while, I had friends who loved me and being in my company. Basically he'd changed, and I hadn't. It gave me the strength to realise that I'd be ok on my own, because I'm actually pretty fab! 😉
I'm just over two years on from all this. It's been a long road. It was so hard, so don't ever believe you are weak for staying. That's bollocks! It takes strength to make any decision in the wake of the shit-storm that's just hit you. That doesn't mean you have to stick to that decision if it isn't making you happy.
We did have counselling - with Relate - individually. Not sure it helped other than giving us the tools to open up and talk about our feelings. DH was a bottler-upper. I'm the opposite but tend to get very fiery and lose my temper.
I honestly didn't start to feel I'd made the right decision for approx a year. It took possibly a year or more for me to stop feeling stressed out about it to the point where we'd have an argument about it every so often. It was suddenly like a switch came on. I feel so much calmer about it all. It happened. DH can't undo it. But he worked bloody hard to make amends and now we're strong and very, very happy.