Dear Prudence Photo illustration by Slate. Photo by Bruno Aguirre on Unsplash. Our advice columnists have heard it all over the years—so we’re diving into the Dear Prudence archives to share classic letters with our readers.   Submit your own questions to Prudie here . Dear Prudence, My husband and I have been married for more than three decades and have grown children and grandchildren. Fifteen years ago, I discovered that my husband had been having an affair with another man for about five years. I was devastated, but my husband and I worked through it and stayed together. We poured ourselves into the lives of our children and grandchildren and now our marriage is better than it was before I discovered the affair. I thought it was all behind us. However, a few months ago, in the middle of the night, I woke up to find that my husband was not in bed. I went looking for him and found him sitting in the backyard sobbing. He told me that he had learned that the man he’d had an affair with had passed away.…