1. Be there or be square
2. Rain or shine
3. Not leave without seeing each other
以上3种都可以表达，而第二种用得最多。第一种是比较老的表达方式。第三种，略显拖沓，不够简明扼要。
举例说明：
Let’s meet at the school this afternoon rain or shine.
我们下午在学校见哦，不见不散。
hey plan to meet each other at the railway station rain or shine.
他们计划好明天在火车站不见不散。
My mum and her friend will meet in Church rain or shine the day after tomorrow.
我妈妈和她朋友约好后天在教堂不见不散。
She and I will meet at the same old place in a month rain or shine.
我和她约好一个月后在老地方不见不散。
英语里面还有很多类似的俗语：
Sleep on it. 意思是等到明天（或以后）再做决定
To wait until next day to make the decision
To break a leg 祝好运
Good luck.
