It is a slow process - we are more than 2 years on and i can totally understand where you are coming from.
Something has gone forever and you must accept that - it is a bit like believing in Santa - once that spell has been broken there is never going back. That precious trust has been shattered and i know a lot of people say that relationships without trust cannot work but i have also leaned that there are many levels of trust.
Some people can not be trusted with money (or to walk past a shoe shop without buying ).
But it is about learning to know at what level of trust you are willing to accept.
Try to focus on the things that are better now - i suspect you talk more and in many ways have a better relationship.
Also dont think that everything will be rosy from now on - and try not to let everything link back to the affair (this is hard and i do think both my h and i struggle with this). You will still have arguments - that is normal.
You certainly have not failed in trying to get over this and give your marriage a chance.
I think you must try not to focus too much on the future - one thing i have learned is that nothing is certain and so now i live much more for today.
I also think you should not say to your h you will never forget - i should think he never will either - but you must now try to have new memories together.
For me a big turning point was when we had a holiday together and i looked across and knew i wanted to grow old with him. But like i say - that may never happen and so i try and live and be happy now.
Also dont put pressure on yourself - if in the future you are no longer happy you dont have to 'stay' married.
Anyway good luck and you are not weak for wanting to do this.