Don't paint the lily.
不要画蛇添足。

【世博精解】

这句谚语从字面意思上理解就是“不要给百合花上颜色。”

lily-one of several types of plant with large bell-shaped flowers of various colors, especially white. It’s often regarded as a symbol of virtue.
百合；百合花。品德的象征。

众所周知，百合是一种非常美丽的花，无需再加以作何修饰，如果再给百合上颜色的话，不就是画蛇添足了吗？

莎士比亚的一段话，不仅生动地解释了“画蛇添足”，而且还给我们提供了许多类似的说法：
"To gild refined gold, to paint the lily, to throw a perfume on the violet, to smooth the ice, or add another hue unto the rainbow . . . is wasteful and ridiculous excess."
-- William Shakespeare

为纯金镀金，为百合着色，为紫罗兰填香，为冰面整饰，抑或是为彩虹增彩，皆属画蛇添足之可笑举动。

In fact, before Shakespeare, it used to gild the rose, or paint the golden rose on church architecture. But rose was later found to have the wrong type of symbolism and was then replaced by the more virtuous lily on the church decoration. And in the 1920s, there was this phrase “gild the lily”, but the more common saying is: don’t paint the lily.

Opportunity seldom knocks twice. 福无双至。/机会难得。

【世博精解】

直译就是机会几乎不会来两次。

Seldom-very rarely.

For example:

She seldom reads newspapers. 她几乎不看报纸。

Knock means strike，敲，击。Twice, 两次。一次就是once, 三次以上的表达方式都是数字加times的形式，比如说：三次，three times; 四次，four times。其实time这个词还有很多用法，比如说我们现在经常用到的一个词“分期付款购买”用英语该如何表达呢？我们可以这样说：a time purchase。

这句谚语告诉我们机会来之不易，我们要时刻准备，等待机遇来临时就要充分利用，否则也会象时间一样一去不复返。