Full Idea
Boredom has been, I believe, one of the great motive powers throughout the historical epoch, and is so at the present day more than ever.
Gist of Idea
Boredom is an increasingly strong motivating power
Source
Bertrand Russell (The Conquest of Happiness [1930], 4)
Book Reference
Russell,Bertrand: 'The Conquest of Happiness' [Unwin 1961], p.37
A Reaction
Most of his essay tells us how to avoid boredom, rather than how it motivates.