From The Diary of Virginia Woolf:

At the moment (I have 7 1/2 before dinner) I can only note that the past is beautiful because one never realises an emotion at the time. It expands later, & thus we don’t have complete emotions about the present, only about the past. This struck me on Reading platform, watching Nessa & Quentin kiss, he coming up shyly, yet with some emotion. This I shall remember; & make more of, when separated from all the business of crossing the platform, finding our bus &c. That is why we dwell on the past, I think.