Guilt is one step away from shame, and shame is almost always toxic. Taking responsibility for your role is different from feeling guilty.
Re: forgiveness, I can tell you in my situation I have decided to let it go. Perhaps one day I will forgive. I feel like the failure of my MR was like a giant boulder dropped into a lake, and the ripples will take a long time to even out, likely years. To me forgiveness is one of those slippery things... the more you think about it, the harder it is to get there. I can see a future where I forgive. I also don't worry about getting there.