My view is not necessarily in line with others, but I decided early on that I had to look at everything that I knew, and if nothing new and detrimental came out, I was going to decide whether I wanted to forgive my H and stay married to him. (If new information of lies, cheating, or whatever came out, this would likely mean instant reversal with a decision to D).
Based on his extreme remorse and his efforts to show me how he wanted to be a man who deserved me for his wife, I decided that I would stay with him. And I knew that meant we would never be happy if I didn't forgive him, so I had to work on that.
Early on, up through two or three months, I would periodically get raging mad at him and scream at him (one reason was because he could not remember the details or what they talked about, and I was frustrated he could not tell me these things). But that had to be part of my decision, all other things considered, did I want to stay married to this man? And so I conscientiously worked on shortening my rages, and getting through some uncomfortable times without raging at all, when I felt it coming on.
I tend to agree with your MC that people need to move forward rather than dwell so much on the past. Of course this only applies if your WS is extremely remorseful, as mine was/is.
My method worked very well for us, and we became closer than we have ever been before. We renewed our vows at 11 months (and I would not have done that if I didn't feel we were healed...I believe in marriage or vow renewal as a celebration of a decision to be together, not as some way to help an ailing relationship).
I'm stuck in this cycle of getting along, making plans and then confronting, arguing etc. How have others got past this phase?
I feel I got past that stage by making a very conscientious effort to stop those cycles of confronting and rage. I don't think five months is too early to do your part in trying to make this marriage better, faster, if you believe she is really remorseful. For me, remorse is the main ingredient for R, along with the BS's willingness to forgive it. Others believe it must take longer, but I don't think it has to be that way, and it wasn't that way for me. We are now going on 7 years out, and are closer than we have ever been.