I used to be a hoarder of cards, letters, and miscellaneous mementos. Then I decided it would be more positive to return the love. You can do this whenever the correspondences align to your liking. I do it at the quarter moon. It is a fire ritual so prepare your fire pit or whatever works in your situation. Gather up all the cards, letters and such that you wish to honor. Prepare yourself and the space as you know to do. Light the fire and hold the items. Walking deosil around the fire, feel the love that the senders put into them. When it feels right, place the items in the fire while chanting something like this:
At quarter moon the fire is lit and upward now the flames do spit
Embers rising in the glow, by my words their purpose know
Cards and letters, mementos dear, from friends and family far and near
I place within this sacred flame that love return from whence it came.
There is more to it, but I think this is enough to give you some ideas. I am happy to respond to any questions.