It's beginning to look a lot like Christmas
[from here]
He looked from the tree to Helen and to the ribbon. "Is there an instructional guide on how to put these things up?" He asked. The Doctor never had to do anything like that before and he'd had enough trouble getting the tree to sit straight up in the stand.
The Doctor focused on Helen, the pensive look in her eyes as she focused on the tree. It truly amazed him how she could give so much with everything she did. She never performed anything halfheartedly. She put all of herself into her work, her family, everything.