If anyone ever asked him what was his happy thought, Stiles would say the first time he caught Derek smiling for no reason at all. By sheer happiness and joy. To be with Stiles, to have friends, to not have awful things happening in his life for once. And that memory is even more special cause he was there to see it. And he wants to burn it forever in his memory, and to paint it on the walls, but at the same time he wants to keep it for himself, sacred, keep it a secret from everybody else. Cause he knows how much it took for Derek to be this relaxed, to finally allow himself to feel positive things without being overwhelmed by the fear of losing everything, to have everything taken away from him in moments.