Just because a person or a pet is gone doesn't mean you shouldn't always remember them. It may be comforting to know that even if the person or pet is no longer here, the friendship, love and personal ties you have with them still exist. No one will ever be able to take that away from you, and the relationship you have with them will always be a part of you. Some mementos will always be worth keeping to remind you of your own courage, tenacity and ability to envision a better future.
Keep the mementos that remind you of the person or pet in a box somewhere out of the way. Bring them out when you need a tangible reminder of your memories. It's not usually a good idea to leave the mementos lying around in the open. A constant reminder that someone is gone can make it hard to move on