1. To make hay while the sun shines （打鐵趁熱）
The idiom "make hay while the sun shines" means to take advantage of an opportunity while it is available or to make use of favorable conditions while they last. The phrase originated from the practice of farmers harvesting hay on dry, sunny days when the hay is more likely to dry quickly and prevent it from rotting. Thus, the phrase is often used to encourage people to act quickly and make the most of a good situation before it passes or becomes less advantageous
"I know you're tired, but we should finish this project while we have the chance. Let's make hay while the sun shines."
"The stock market is doing well right now, so it's a good time to invest. You should make hay while the sun shines."
"We're going on vacation next week, so let's finish all our work before we go. We need to make hay while the sun shines."
2. Once in a blue moon （鮮少地、罕見地）
Blue moon不是字面上的藍月，而是形容同一個月分當中，出現的第二個滿月。按照慣例，我們每個月都會見到一次滿月，由於我們在日期上只有一天一天，沒有所謂0.5天這種數字，再加上有些月份30天、有些31天，按照精準計算，滿月大約每 29 天發生一次，因此偶爾一個月會有兩次滿月。根據NASA計算，大約每隔兩年半會發生一個月內出現兩個滿月。據說今年2023年，8月底有機會出現Blue moon！
也因為每兩年半左右，才會出現一次這樣的現象，所以才衍伸出了Once in a blue moon這樣的用法，有點類似成語「鐵樹開花」，形容少見、難得一見的現象。
The idiom "once in a blue moon" means something that happens very rarely, almost never, or very infrequently. It refers to the occurrence of a second full moon within the same calendar month, which is a relatively rare event. A blue moon is not actually blue in color, but rather a term used to describe the rare phenomenon of two full moons appearing in a single month. This idiom is often used to describe an event that is unusual, unexpected, or happens only very occasionally
"I only see my old college friends once in a blue moon, since we all live in different parts of the country now."
"I don't usually go out to eat at fancy restaurants, but I decided to treat myself once in a blue moon."
"The last time we had a snowstorm like this was once in a blue moon, over a decade ago."
3. Written in the stars （命中注定）
講到星星，就不得不提家喻戶曉的兒歌小星星，小星星的歌詞是一位英國女詩人，Jane taylor於1806年所發表，描述他眼裡看到的星星。雖然是一首來自英國的兒歌，但它的旋律卻是來自18世紀的一首法國童謠，同樣的旋律也被應用在了Alphabet Song。
The phrase "written in the stars" refers to the idea that fate or destiny has already predetermined a certain outcome or event. It suggests that something is inevitable or unavoidable, as if it has been written in the heavens. The origin of the phrase can be traced back to ancient beliefs about astrology and the idea that the positions and movements of the stars can influence human affairs. In modern usage, the phrase is often used to describe the feeling that something is meant to be, or that a certain outcome is inevitable, even if the reasons for that feeling are unclear or unexplainable
"Even though we come from different backgrounds and have faced many obstacles, I know that our love is written in the stars."
"The success of their business seemed to be written in the stars, as every decision they made seemed to lead them closer to their goals."
When they first met, it was like they were destined to be together - their connection was written in the stars.
"Some people believe that their life path is predetermined and written in the stars, while others believe that they have the power to shape their own destiny."