Have a lamp with a bright steady flame or a candle before you. Sit in the Padmasana posture or any other comfortable asana in front of the flame. Look at the flame steadily. Then closing your eyes, try to feel the flame inside you, between your eyebrows. From there let it descend down into the lotus of your heart, in the centre of the chest, illumining the path.
When it enters the heart, imagine that the petals of the lotus bud open out, one by one, bathing every thought, feeling, emotion and impulse in the light and so removing darkness there. There is no space now for darkness to take refuge. It has to flee before the flame.
Imagine that the light becomes wider, bigger and brighter. Let it pervade the limbs; now these limbs can never more deal in dark, suspicious and wicked activities. These have become instruments of light and love.
Let the light reach up to the tongue and falsehood, slander and spite vanish from it. Let it rise up to the eyes and the ears and destroy all the dark desires therein. Let your head be surcharged with light and all the wicked thoughts flee therefrom, for these are the denizens of darkness. Imagine that light in you more and more intensely and it will become so. Let it shine all around you and let it spread from you in ever widening circles, taking in your loved ones, your kith and kin, your friends and companions, your enemies and rivals, strangers, all living beings, the entire world. Stay on in that thrill of witnessing light. If you are adoring God in any form, now try to visualise that form in the all-pervasive light, for light is God and God is light.