Reflect on all your experiences over these years, I believe you should find that there's still a lot of beautiful memories between you. Memories that we have never experienced, and do not know what such memories feel like.
Grandfather, I know that such events are an enormous insult to a man, a deep humiliation, a shadow that may never be erased in a lifetime. But I believe, as long as you sincerely want to live on with grandmother, no matter what mistakes she has made, you can forgive and tolerate.