It's hard to shift gear when you come home after a busy day at work.上班忙了一天后回到家里很难回过神来。It's difficult to steer and change / shift gear at the same time.很难一面操作方向盘一面换挡。He shifted gear and tried for the throwaway approach.他变换思路，尝试即兴方法。The speaker suddenly shifted gear.演讲者突然改变了调子。