【聯合報╱執筆／台科大應用外語系助理教授黃玟君】
這句諺語直譯是「機會只敲一次門」，句中的but是副詞，意為「僅僅…，只是…」。此句通常用來勉勵人把握機會，因為機會若錯失了，可能永不復返。這句話也可寫成：Opportunity seldom knocks twice.（機會很少會敲兩次門）。那麼要如何抓住機會呢？當然必須事前做好所有準備，這也是為什麼有人說：努力的人不一定會成功，但成功的人一定有努力。
實用對話Conversation
A: I received an admission letter to the Harvard University School of Business... full scholarship, too!
B: Congratulations! When are you flying out? We should throw you a farewell party.
throw a party（口語）舉辦派對
A: But I'm still unsure as to whether or not I want to go study there...
B: Why? This is practically a gift from heaven!
practically (adv.)（口語）幾乎；差不多
A: But my ex left me while I was serving out my military service, and I'm afraid that the same thing might happen again.
B: Opportunity knocks but once. Seize the opportunity. Stop being so indecisive!
indecisive (adj.) 優柔寡斷的；無決斷力的
