In the following year, 1930, I published The Conquest of Happiness, a book consisting of common-sense advice as to what an individual can do to overcome temperamental causes of unhappiness, as opposed to what can be done by changes in social and economic systems. ... What I do know is that the book was written at a time when I needed much self-command and much that I had learned by painful experience if I was to maintain any endurable level of happiness.
Source: The Autobiography of Bertrand Russell, v.１, chap. 6: Principia Mathematica, 1967.
More info.:http://russell-j.com/beginner/AB16-090.HTM