恰恰是好的事物会带来不好的一面（双刃剑，一个硬币的两面？）；
也就是说，快乐和满足总会带来其他的欲望，而一定程度的痛苦却反而会浇灭这些欲望。
——叔本华《论世间苦难》
“on the suffering of the world” arthur schopenhauer states:“it is the good which is negative; in other words， happiness and satisfaction always imply some desire fulfilled， some state of pain brought to an end.”