When stocks are attractive, you buy them. Sure, they can go lower. I've bought stocks at $12 that went to $2, but then they later went to $30. You just don't know when you can catch the bottom.

科学进步的关键是坚持和开放的心态。

乐观是一种创造更美好未来的策略。因为除非你相信未来会更好，否则你不太可能站出来为创造这样的未来承担责任。