Disclaimer: I own nothing :v
"Memory"
Memories are tricky things. Theo once found pictures of him and Blaise as small kids on the other's trunk, but as much as he tries, he can't remember what or when it had happened. On the other hand, there are the memories burnt into his mind that he can't get rid of, like the day his mother was laughing at some story he told her and she suddenly just fell on the ground, never to manage to get up again.
He knows, he knows that those early memories that he can't remember are with him just as much as those which taint his dreams sometimes, that he just can't trigger them to remember, or he can't seem to forget the others.
But memories are good too. They're good when he looks over Malfoy and contains a laugh over the small boy who claimed to be King Of the Dorms, or when he sees Crabbe and Goyle and remembers to let some pie over lunch for them because he knows how much they like it. When Daphne smiles at him and he chooses to remember his only friend, instead of the girl who betrayed him, once. When he looks at Bullstrode and is on alert, knowing to be careful around her.
When he looks at Blaise, and smiles and is happy, and thinks that that is a moment for later to remember, for when there is doubt he can look back and think 'this, this is why I love him'.
Then memories are great.