胸有成竹
What does 胸有成竹 mean?
To have a complete picture fully formed in your mind before you act — to move from thorough preparation, not guesswork
比喻做事前已经充分观察、思考和准备好，心里早就有了完整清楚的打算。
Historical origin
In this story, the painter Wen Tong ignores the practice sheets and takes Chen Ying to Yundang Valley to quietly observe real bamboo. Back in the studio, Wen Tong waits with his brush over blank silk until the whole bamboo is clear in his mind, and then he paints it in sure, living strokes. Later, Su Shi writes the line that explains Wen Tong's method: to paint bamboo, you must first have the whole bamboo formed within your chest.
How do you use 胸有成竹 in a sentence?
Before building the model bridge, Maya studied the plan so carefully that she was 胸有成竹 and finished it with confidence.
在搭建模型桥之前，玛雅把设计图研究得非常仔细，所以她胸有成竹，很有把握地完成了它。
Common mistake
A common mistake is using this idiom for someone who is only pretending to be confident. It is wrong because 胸有成竹 means real confidence based on full preparation, not empty boldness.
一个常见错误是把这个成语用来形容只是装作很有信心的人。这样不对，因为"胸有成竹"指的是建立在充分准备上的真正有把握，不是虚张声势。
More examples and usage guide