One of my luckiest instincts lay in being able to tell when I was happy— at the time, not afterwards. Most people don’t realize until long afterwards that they have passed through a period of happiness. Their enjoyment takes the form of reminiscence, and it is always tinged with regret that they had not known at the time how happy they were. But I knew, and my memory (of bad times too) was detailed and intense.
Paul Theroux, My Secret History
memory, self-knowledge, time