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.
粒子的概念只是一种近似，仅在特定极限情况下有效。
The world is always ending for someone.
The wise are not ashamed to seek knowledge, for they know the ocean of wisdom is boundless.