Each problem that I solved became a rule which served afterwards to solve other problems. (Rene Descartes, Discours de la Methode)

An inconvenience is only an adventure wrongly considered; an adventure is an inconvenience rightly considered. (Gilbert Keith Chesterton)

Some cause happiness wherever they go; others, whenever they go. (Oscar Wilde)

Once is happenstance. Twice is coincidence. Three times is enemy action. (Auric Goldfinger, in Goldfinger by Ian L. Fleming)