上一次当，学一次乖

Fall into the moat and you'll be wiser next time (idiom); One only learns from one's mistakes.

lit. the cart in front overturns, a warning to the following cart (idiom); fig. draw lesson from the failure of one's predecessor; learn from past mistake

to learn from experience (coll.)

once bitten by a snake, ten years in fear of a well rope; once bitten, twice shy (idiom)

to draw a lesson (from a setback)

lit. you can't gain knowledge without practical experience (idiom); fig. wisdom only comes with experience