Who said "complaining about others and preventing heartbroken"? What's the next sentence?

Mao Zedong, the next sentence is "When you have a good prospect, you should be observant".

The full text is as follows:

Seven Laws and Mr. Liu Yazi (1April 29, 949)

I can't forget that when I was drinking tea in Guangdong, I was talking about Ye Huang Zheng in Yuzhou. Thirty-one years after returning from my motherland, I read zhanghua when the flowers fell. Complaining too much can prevent heartbroken, and you should pay attention to it after a long history. The water in Kunming, Mo Island is shallow, and watching fish is better than Fuchun River.