Get as comfortable as you can, close your eyes, and seek that place in yourself that feels connected to the divine. Breathe deeply and slowly for a minute or so, making sure that your exhalation completely empties your lungs. Allow yourself to just relax a little more every time you exhale.
Inhale slowly, thinking "Serenity". Imagine as you inhale that you are drawing serenity in with the air. Hold for a moment, envisioning your tissues absorbing the serenity you took in, as it takes up the air, then exhale, allowing your breath to carry any stress out with it.
Following the above steps, inhale slowly again, thinking "Faith". As you exhhale, allow distrust to exit , your body through your lungs.
Repeat, this time thinking the word "Love". And this time, exhale hatred and fear along with the expended breath.
The final word of the mantra is "Peace". Follow the above steps, and allow your body to exale any non-peaceful feelings.
Repeat as needed, and hopefully, you will feel tension leave you, and relaxation seeping in through your pores. If the words I mentioned above don't work for you, try other combinations of words - whatever will make you feel better.