having a plan is a metaphor for being skilled and sure. "Have a plan" and "have a plan" both mean "have a plan in mind". However, "having a clear plan" focuses on having a comprehensive consideration and solution to the problem beforehand, or acting calmly and calmly because of having an idea in mind; "Know what you know" focuses on understanding the objective situation and is very sure.
Source: Song Su Shi's "Literature and Paintable Bamboo in the Valley": "Therefore, if you draw bamboo, you must first have it in your mind."
Wang Xizhi, a famous calligrapher in the Eastern Jin Dynasty, began to practice calligraphy when he was seven years old. He practiced calligraphy very hard, and often practiced calligraphy by the pool, and the water in the pool was dyed black. At the age of 33, he wrote Preface to Lanting Collection, and at the age of 37, he wrote Huang Tingjing. Later, due to the replacement of the writing board, the craftsman found that Wang Xizhi had a strong brushwork and his handwriting had penetrated into the board for three minutes. Later, it was used to describe the vigorous brushwork of calligraphy, and also to describe the profound and accurate opinions and arguments. Volume 87 of Shuo Clan quoted Zhang Huaiguan's Shu Duan Wang Xizhi in the Tang Dynasty: "Wang Xizhi's book is a blessing edition, and the workers cut it, and the pen is incisive."