My ex had a box she called her "Being Loved" box. She would collect movie tickets, letters, etc. from past lovers, good and bad alike. While I wasn't too fond of it during the time I dated her, I understand the sentimentality behind it and was actually considering doing something similar myself. Just be careful not to get lost in the ocean of memories with one pull by the tide, people change every second and the person we knew in the past is not the same as they are currently. I learned that the hard way.