瞎忙活，徒劳无功
You help your dog chase its tail.───你帮助你的狗追它自己的尾巴跑。
If you don't want your image tarnished, chase your tail before you get into serious trouble.
chase your own tail───追你自己的尾巴
change your tune───改变你的调子
chance your arm───试试你的胳膊
chase mortise───榫眼
chase the ball───追球
leave your mark───留下你的印记
lose your cool───失去冷静
lose your grip───失去控制
lose your rag───把你的破衣服丢掉