The community refers to the person who had been being trained to be the Receiver (Rosemary) as a failure because she had been unable to deal with the pressure of getting all these memories. She had been unable to handle the pain, among other things. Because of this, she asked to be released. The way the rules were, she had this right and they had to release her.
This caused a great deal of trouble because of the memories affecting the community. Because of this, the rules were changed and Jonas was not allowed to ask to be released.
As was mentioned in the previous post, the community refers to the former Receiver-in-training as a failure because she was unable to follow through with her assignment. Unfortunately, Rosemary could not deal with the overwhelming negative memories and asked to be released. When Rosemary died, her negative memories spread throughout the community, causing chaos and discomfort. The Elders adjusted the rules concerning the next Receiver so that another terrible incident could be avoided. Unlike Rosemary, Jonas is not allowed to request release during his assignment. Fortunately, the Giver understands the importance of gradually introducing difficult feelings and sensations to Jonas after his previous experience with Rosemary. Slowly, Jonas experiences various painful memories at specific times so that he is able to deal with them. In Rosemary's case, she was not able to bear the weight of the negative experiences and chose suicide over her assignment.
Rosemary, the Giver's natural daughter, had been trained to receive the memories. She too had been given them slowly with the happy ones first. However, when the Giver gave her the memory of loneliness she could not handle it. It had been too much for her and she had asked to be released.
Once Rosemary was released the memories returned to the people and they suffered and did not know what to do. As a result the rules changed. The person who received the memories could no longer ask to be released after obtaining the memories.