When you get tired from all that walking, there are more than nine thousand benches where you can sit down.

VOA: special.2009.10.30

When you're really tired sleep is what you want to do like when you're really hungry you want to eat.

你累了，就会想睡觉,正如你饿了想吃东西一样。

耶鲁公开课 - 心理学导论课程节选