They must often change, who would be constant in happiness or wisdom. Those who continually search for happiness will never find it. Happiness is made, not found. To be without some of the things you want is an indispensable part of happiness.
Bertrand RussellI think it would be just to say the most essential characteristic of mind is memory, using this word in its broadest sense to include every influence of past experience on present reactions.
Bertrand Russell