This is a handy exercise to use when you have that feeling of negative energy coming toward you.  (1) Stand facing the direction from which danger is apprehended. (2) Visualize your special sign of spiritual protection (cross, pentagram, Star of David).  Visualize it in the center of your forehead as strongly and brightly as possible. (3)  Raise your arms in front of you, the backs of your hands facing you.  Bring the tips of your two forefingers together and the tips of your two thumbs, so as to form a triangle.  (4) Raise your two hands together so that the backs touch your forehead, this triangle should be framing your visualized protection symbol.  Pause for a moment.  (5) Utter silently or out loud, a divine name so that its power may activate your visualized symbol (your spiritual guide, an archangel).  (6) Suddenly, fling out your arms before you, hands parting and fling the visualized symbol forth with that gesture, toward the menace.  Visualize the flying symbol bursting into a blazing brilliance and you will have your space to perform the Tower of Light protection as follows: (1) Breathe deeply and evenly.  (2) Progressively relax your entire body.) (3) Stand erect without stiffness, arms at sides.  (4) Visualize all about you a long ellipsoid of intense bright blue light.  It extends about nine inches beyond the surface of your body all around, and about sixteen inches above your head and below floor level at your feet.  (5)  When you can visualize or are aware of this well-defined field of intense bight blue light entirely surrounding you, visualize within the summit of that aura, slightly above but not touching your head, a globe of brilliant white light.  (6) Concentrate your attention on this globe so that it becomes brighter, glowing white like burning magnesium.  (7) Be aware of these two images: the intense bright blue ellipsoid in which you are entirely contained and the effulgent white globe over your head. (8) Aspire to the highest good you are capable of conceiving.  (9) When you feel ready, see that dazzling globe sending down glittering white light.  This light is filled with silver sparkles and floods your aura while also coursing vibrantly through you.  (10)  The outer shell of your aura remains sharply defined as an ellipsoid of intense bright blue light filled with vibrant, sparkling, white light.  (11)  Continue this visualization as long as you can effectively concentrate upon it.  Source  Psychic Self-Defense by Denning & Phillips.