The benefit of forgeting

Memory is so important. We all want to improve memory. We hope we can remember everything we see, hear, experience. However, sometime forgeting is better than memorizing.
Today, I talked to a lady in a Church. I told her that I am a person who stutters. He told me that she was a person who stutters before and now she almost recovered in everyday comversation.She told me the story about her stutter. I talked with her about 5 minutes.  She did not show any stuttering phenomena during the conversation. She told me that she had therapy at about 8 years old. The speech therapy helped her a lot. When she was in her twenties, she had been hypnoticzed. Once she was hypnotized, the hypnotist helped her to forget her stutter. Now, I think she should be in her early fifties.  She told me that to forget stutter is the key for overcoming stuttering. She told me that she is still afraid of using telephones and afraid of speaking in public. She is ok in everyday conversation.
How can I develop such forgeting?
There are many other situations (unpleasant) that forgeting is better than memoring:
I hope I have the power to forget what I wante to forget, to remember what I want to remember.