I'm in year 6 of R and here is what I can tell you about my experience and opinions on self-forgiveness, and on the shame and regret that usually keeps us there.
Am I unusual? Are there any tricks to letting things go and forgiving myself?
No, you aren't unusual at all, in fact, I'd say most if not all of the WS's I've spoken to over the years feel exactly the same way as you do, and I count myself among them. In fact, I'd be much more worried about you if you DIDN'T feel like a POS. It at least indicates an ability to recognize your own disappointment in yourself, and hold yourself accountable for the things you've done. So take a moment and reflect on that. If you ever take a look at Charles Manson, you'll see "crazy" in his eyes. No regret, no remorse, no sense of "Holy ****, I killed people"... he is a sociopath (well, that's up for debate, but I digress). We cannot change what we cannot acknowledge, so if you are seeking to be a better person, someone you can love and respect more, then you have to start with what you don't love. That's where you are now.
The truth is that the things you did, are frozen in time. We can't go back and undo those things. We can't "make them better". While we can learn lessons from them, there will never be a time when we look back and feel differently about what happened or ourselves at that moment. What we did WAS unforgivable. We need to accept that reality at its face value.
But imagine this. Imagine that you and another person get into a car accident. The other driver gets out of his car, puts his head in his hands and weeps. He tells you what a horrible person he is for hitting your car, examines the damage done and cries more and more. You ask him for help and he weeps. You ask him for ID and he says he's too overwhelmed to look for it. He says he's sorry, he mourns uncontrollably, he pounds his head against the car door and keeps saying what a loser he is. And while all of those things may or may not be true, the fact is, all of his weeping and shame and hysterics are about as unhelpful as they could possibly be. Should he feel bad? Of course! But it accomplishes nothing. It changes nothing. And it leaves you, the person who was hurt, to pick up all the pieces on your own, except that now, you also have to deal with the weeping baby that just hit you in the first place. It actually makes things WORSE, not better.
Now imagine that the guy who hit you gets out and immediately checks to see if you are okay. Even though he's at fault, he takes photos of everything, calls an ambulance for you, calls the cops to come investigate the scene, and makes sure to send you copies of his insurance and ID to your phone on the scene. He offers to pay for all damages to the car and also to pay any medical bills you might incur as a result. He pays for the car to be towed and fixed. Later on, he takes defensive driving courses and takes up meditation and yoga with the goal of learning to be more present and calm while driving in the future. He calls you every few months just to check in and make sure that you are okay and that you have what you need to get around while the car is being fixed.
Now let me ask you... how do you feel about the guy being a weeping baby who can't get past his own fuckup long enough to even lift a finger or show some empathy or accountability?
How do you feel about the guy who took ownership from the get-go, took steps to correct his actions as best as he could, put your needs front and center ahead of his own, and took additional steps just to make sure it never happened again?
When we get stuck in our shame, we end up being the first guy. We see a LOT of "first guys" here. They cry and tell everyone how sorry they are and what a POS they are, but that's it. They think that feeling bad is somehow what they need to do, all they need to do. It's reasonable to feel overwhelmed by your own bad choices and actions, but feeling bad serves little to no purpose other than to serve as a guide and a motivator for what to do next. We can either do something about it, or do nothing about it. Feeling sorry about it is great for TV and movies, but in real life, you need to either shit or get off the pot.
The way you learn to forgive yourself is by earning back your self-worth. You got into trouble by making poor choices and actions, you reverse that the same way. You make better choices. You take better actions. And you make changes within yourself in order to make better choices moving forward.
I will never, ever, ever be okay with what I did to my wife, my family, and even myself. It's unforgivable, it just is. But I also see it as a "point in time". It is "part of my story", not my entire story, as that story is still being written. I get to decide how that story goes moving forward. I can either be the guy that feels sorry for himself (btw, that was me for about the first 4 years of R, and it did so much more damage to our R than was necessary) or I can be the guy that owns it and does all he CAN do to make things right as best he can. I can't undo what I did, but I can do a whole lot better moving forward. I can't unhurt my wife, but I can treat her with the love and respect she deserves moving forward. I can't forgive my bad actions, but I can offset them with much better actions. I can hate who I was but love who I am. Does that make sense?