Good luck doesn't always repeat; a method or lucky break that worked once won't necessarily work again.
宝くじに当たったからといって同じ方法でまた当たるとは限らない。柳の下にいつも泥鰌はいないよ。
Just because you won the lottery once doesn't mean you'll win again using the same method. Luck doesn't always repeat.
その商売が一度成功したからといって同じ手が通用するとは限らない。柳の下にいつも泥鰌はいない。
Just because that business succeeded once doesn't mean the same trick will work again. Good luck doesn't always repeat.