work my ass off :【拼命工作break(或 bust)one's (sweet) ass: 拼命干】
I was working my ass off when my boss kicked back in the pub.
我玩命地工作的時候我老板竟然在酒館里悠哉游哉。
on second thought: 仔細想想
I said I wouldn't do it, but on second thought I think I will.
我說我不會做此事,但再細想一下我想我是會做的。
He have intended to go, but on second thought, he give up the idea.
他本來想去,但進一步考慮後,打消了這個念頭。