He is on his high horse these days.

他最近几天很嚣张。

　　词组 be on one's high horse 指的是趾高气扬、目空一切、盛气凌人的那种状态，用中文的“嚣张”来表达比较贴切。

　　例句：Joe seems to be on his high horse these days. This is "When the cat's away, the mice will play".
　　乔这几天很不可一世，正应了那句“猫不在家，耗子成精”（“山中无老虎，猴子称大王”）。