Well, I think it depends on whether you and he are single now, whether you want to save this relationship or just want to be friends.

If you want to save your feelings, I think you should send something with memories. For example, you once said that you would go to Paris together and give him a decoration of the Eiffel Tower, and attached: I'm afraid I won't have a chance to go with you again ... and so on ...)

If you are just friends, don't give anything that will cause misunderstanding, it's just a simple thing, or nothing at all.

But if you are not single, I think it is better not to send this, which will cause unnecessary trouble ... you know ~