Something that boosts one's spirits. Example: When I got my promotion is was quite a shot in the arm.

a shot in the arm Informal Meaning: You can say something is a shot in the arm if it gives a person or an organisation renewed energy or enthusiasm. For example: Getting a grant from the Arts Council was a much-needed shot in the arm for the orchestra. We all agree that the economy needs a shot in the arm, but we can't agree on exactly what it should be. Origin: Related to the medical practice of injecting drugs into sick people. These injections are sometimes called "shots" and they are often administered into the arm. http://www.englishclub.com/ref/esl/Idioms/S/a_shot_in_the_arm_481.htm

help wake u up

I think it is equal to "encourage" or "inspire".