I’m a little bit anxious so this is something difficult. To help calm down, I used to focus on breathing, to trying to lower my heart rate.
I usually use the Meditopia app. It's an incredible app for all the moments even for the good or bad times. Using the app you learn to see yourself internally and starts to pay attention on your breathing.
And last but not least I go to the gym. Working out always lifts my mood and makes me feel better.