jump in and get one's feet wet
事到临头打退堂鼓，出现cold feet 的现象也许是一个弱点，
但是在美国成语里，把脚弄湿倒是一件好事。
比如说，许多初学的人都怕难为情而不敢用英语来对话。
可是，老师很可能就会劝这些学生：jump in and get your feet wet
这个俗语的意思是：到实践中去学
也可以说是跳到游泳池里学游泳。
e.g.i know most of you are afraid to embarrass yourselves by trying to speak english after these first few lessons.but that's the best way to learn: when you meet an american, try a few words--jump in and get your feet wet.
我知道你们大多数人感到刚上了几课英语，就用英语来说话很不好意思。不过，当你见到美国人时，你不妨试着说一点。到实践中去学是最好的办法。
又如：i want to get into politics so i'm volunteering to put up signs for one of the people running for mayor.i don't get paid for it but it's a chance to jump in and get my feet wet.
我希望将来能够到政界去工作，所以我现在在帮一个竞选市长的候选人张贴宣传标语。我帮他做这些事是完全义务的，没有工资的。但是，这是到实践中去得到一些经验的好机会。