To mountaineers, the toilsome activity of crawling over slippery rocks in foul
weather is not inherently joyful. It is the self-satisfaction derived from the
personal triumphs over lofty peaks that provides the exhilaration. Remove the
personal challenges, and crawling over rocks becomes quite boring. It is people's
affective self-reactions to their own performances that constitute the principle
source of reward, (p. 216)