Making the sign of the cross acts as protection. The cross symbolizes the powers of the four elements and can act as a shield and berrier.
Bad energy tends to go right to the stomach, so when you have to deal with hostile people, or have a bad experince draw your fingers acorss your upper and lower abdomen and make a small equal armed cross. Repeat the motion several times, while visualizing a shield of protective energy building in front of you.
Then rub your palm around the area in a circular motion unitll you feel more relaxed. If you have to confront negativity on a reular basis, hand a Celtic cross on a very long cord, and wear it beneath your shirt posistioned about your navel.