Change a feeling question

A relationship I was in ended. It was a relationship I cherished. For the first time I felt true joy and happiness with this person. I’m struggling with changing how I feel. Some days I’m in different realizing the relationship ran it’s course and we both needed to move on to the next phase our of lives. Most days I am sad this person is not in my life. How can I use the model to change my feelings and thoughts about the break up and about this person? I can’t seem to keep the sadness and anger from coming back.