Paying attention to the world around you can help ground yourself into the present to get you out of your mind and away from stress. Here is a great grounding technique to help calm your mind. Below is a link to other tools you can use to help you destress throughout your day.
Doing some deep breathing can help calm your brain and slow your body down to help you relax. Here are some deep breathing techniques to help calm your mind and your body.
Here are some cool apps that you can download on your phone. They range from meditation to general mindfulness techniques.
Headspace
Three Good Things
Insight Timer
Smiling Mind
Calm
My.Life