When your breathing and mind are racing away, you can feel it's out of control. That's not true.
A simple technique is alternative nostril breathing.
Using your index finger your left hand close off your left nostril, take a slow deep breath in and out.
Let your mind focus on your breath. Repeat 3 times.
Change to right index finger and right nostril and repeat 3 times.
You may like to try to breath in through one nostril and out through the other.
This will slow and improve the quality of your breath and calm your mind