just what the doctor ordered字面意思正是大夫说的，引申为正合我意；对症下药。

【例句】
That meal was just what the doctor ordered, I hadn't eaten a thing all day.
那顿饭菜正合我意，我已一整天没吃东西了。

Ooh thank you, a nice cup of tea, just what the doctor ordered.
谢谢你，这茶真好，这正是我需要的。