(This isn't my memory; it's one of Seven Answers).
I have a very strong memory of being five or six, at Christmas time. We lived in a big, old townhouse, three floors high with massive staircases and creaky wood everywhere. At Christmas we'd have a huge Christmas tree in the hall, covered in multicoloured lights, little carriages (like old fashioned horse carriages) with lights inside. In the morning, when it was still dark, Dad and I would creep downstairs, crawl under the tree and turn the lights on. I don't know why it was the two of us, as we have a big family, but in all the excitement and clamour of Christmas it seemed a really precious, almost sacred time, just the two of us in the cold, dark winter morning.