the shot in the arm 激励；鼓舞

A：Good news!
B：What is it?
A：The state of economy is starting to go up in our country.
B：That’s just the shot in the arm we need.

A：好消息！
B：什么消息？
A：我们国家的经济状况开始好转了。
B：那正是我们所需要的鼓舞人心的消息。