She took a deep breath and prepared for the challenge.

Meaning: This means to breathe in a lot of air, often to calm down or prepare for something.

Choice of Words: Deep means something that is very low, or that extends far down. Breath means the air that you take into and out of your body. When you put them together, "deep breath" means to take in a lot of air, which is often done to calm down or prepare for something.