Nicole Le Pera is a psychologist based in Philadelphia, who has recorded this 16 minute meditation for times of stress. 

Her instructions are: "Make sure you do this in a space you feel safe and won’t be interrupted. You can sit up, lie down, or be in any position you feel comfortable in. As you meditate, try to slow down your breathing and relax your body. You mind will wander— and that’s ok! Stick with it and gently guide your mind back. Meditation is a powerful way to teach our body that we’re safe. Try to practice this meditation a few times, and you’ll notice how much more relaxed you are after each practice."

 
You can find out more about her work, here