Hi Pei Yung - you've picked up some great idioms there:-) 'wait and see' and 'take one day at a time' are both very common in British English. 'let the chips fall' is less common - I've never used it, anyway. Your sentences would sound more natural like this: I have no idea whether I can get a job or not. All I can do is try my best and just take one day at a time. All I can do is wait and see. All I can do is try my best and let the chips fall where they may. Hope this helps - have fun learning English.

No, they're all different. . You can say all of them in that situation, but the meaning is still different. In other situations you can't use all of them. Nothing is interchangeable with anything else! :)