r366-c014
過剰に興奮に満ちた生活は,心身を消耗させる生活であり,そこでは,快楽の必須の部分と考えられるようになったスリルを得る（自分に与える）ために,絶えずより強い刺激が必要となる。
A life too full of excitement is an exhausting life, in which continually stronger stimuli are needed to give the thrill that has come to be thought an essential part of pleasure.
From: The Conquest of Happiness, 1930, chap.4:Boredom and excitement
http://russell-j.com/beginner/HA14-040.HTM#r366-014