Proust's Lost Time: First Impressions...

You can be possessed so completely by a single emotion at a particular period of time, say, happiness, love, longing, that it is impossible to think of the other states, anger, anxiety, fear, that may possess you as completely at other times in the same day. Time, thus, gets divided not by the hours through which it passes, but by the feelings and moods and emotions that are ephemeral and that are evoked by different states of your own nature and your environment.

A terrific insight, which, as with all great isights, one feels one always knew but had never found the words to express or recognize it clearly within one's own experience. To me, nobody had quite expressed this so clearly and so beautifully until I read Proust.