He used to have an untidy appearance. After several failed attempts to ask a girl out, he finally learned his lesson and spruced up his appearance.
learned one's lesson (the hard way)the hard way 就表示親身經歷錯誤而學到乖, 這是正統的美語說法.
他之前往往不修邊幅, 後來經過多次跟女生約會失敗後總算學到教訓, 開始整理自己的儀容了
這是一個連環問題: 燃燒石油導致二氧化碳增加，二氧化碳增加導致溫室效應，溫室效應導致冰層融化、海平面上升。 (請填空)
This is a chain of problems. Burning oil leads to increase in carbon dioxide, which leads to the greenouse effect, which leads to melting of glaciers, which leads to rising sea levels.