"The Analects of Confucius. Taber recorded Ceng Zi's words: "Ask if you can, ask if you can't, and be honest with Xu Ruo if something happens." Only an open-minded person can do it. And Ceng Zi said another passage, "A scholar has a long way to go to strive for self-improvement", which needs it.
Only those who are strong-willed, able to shoulder heavy burdens and struggle for a long time can do it.