Coming Up For Air - George Orwell

The past is a curious thing. It's with you all the time. I suppose an hour never passes without your thinking of things that happened ten or twenty years ago, and yet most of the time it's got no reality, it's just a set of facts that you've learned, like a lot of stuff in a history book. Then some chance sight or sound or smell, especially smell, sets you going, and the past doesn't merely come back to you, you're actually IN the past. It was like that at this moment.