This is one that I've been using for years. I've shared it before, but I know that I keep coming back to this practice for a reason - it works every time, no matter what discomfort I feel.
Sit comfortably for 60 seconds and locate where you are storing discomfort or tension in your body.
For me, it is most often my stomach. Your gut is great to practice this with, as the chakra located around your stomach is called your "Manipura," or city of jewels, and helps balance your self-esteem.
Imagine your discomfort as a ball of color. Usually I stick with dark, ugly colors, like green, yellow, black, sometimes red. It is the color I imagine my feelings taking on. It helps transform my emotions into a tangible visual.
On the inhale, breathe that color from where you are storing it up into your throat.
On the exhale, release it out of your mouth, and allow the color to transform to a beautiful stream of pure white light.
Mostly importantly, allow that light to reenter your body at that uncomfortable place, replacing the negative.
After a few breaths of breathing out the bad, breathing in the light, you are guaranteed to feel a little more healed, a little stronger, and even a little healthier.