Unique bond broken

My husband had an affair with a good friend of ours. Her husband was his best friend since high school. We also started our relationship at 14. He claims that what made him want to have the affair was curiosity since he had never been with anyone else. The other couple was in the same situation. They thought it would be safe since they were just friends and neither ever wanted to leave their spouse. Of course, things changed once they started the affair. I always felt that the fact that we had only ever been with each created a very special bond. We are trying to make it work. We have been married for almost 28 years. The loss of the bond is on my list of losses to be grieved but ultimately accepted.