Focus on your breathing by following the ball: https://mindfuldevmag.com/breathing-timer/breathing-timer-gifs 

Guided meditation and guided imagery can help to clear your mind when you are overwhelmed:
https://www.youtube.com/watch?v=AbckuluEdM0&list=PLT90E4KhnNhs44PXJzIn0euFPa2j_Q217
https://www.youtube.com/watch?v=ez3GgRqhNvA