There are three stages of sadhana (spiritual practice). They are concentration, contemplation and meditation. Concentration entails fixing your gaze on one form. Contemplation occurs when you are able to perceive the form within you, even in its absence. Meditation means when, as a result of this exercise, this form is permanently imprinted in your heart. If you continue to meditate in this manner, the form will constantly be fixed in your heart. You should not confine your spiritual practices only to concentration and contemplation. While it is true that these are the first steps in your spiritual practices, you must progress further; you must transform concentration to contemplation, and then contemplation into meditation. When you carry this out, you will continue to visualize the form of God at all times. The ancientrishis (seers) adopted this form of meditation. That is why God manifested before them whenever they wished, talked to them and fulfilled their desires.