Since a few days whenever I sit for meditation, after the thoughts cease and I am only aware of the breath going in and out, suddenly I feel a presence, other than me and there is an awareness of this presence. I continue watching the breath but there is a presence other than me. Sometimes when I continue longer, it disappears when there is not even awareness of breath. I am not able to understand why it happens so? Please enlighten.

This presence is complete separation of the mind from the body and reverting back to conscious existence where the witness-hood (Sakshibhava) ends and the sakshi alone is. The consciousness alone remains without effort to be a sakshi. This state remains as long as the efforts are not added to this experience. But if the efforts are added again the body identification begins.

This is the Rasa Leela of Lord Krishna. When on the sharad poornima the gopies became aware of their separate identity from the Lord, and began to think how lucky they were than others, the presence became present (i.e. the mind) and they were miserable. But when that misery of separation was so intense that again it disappeared along with their efforts. When they ceased to exist as gopies, the Lord was revealed.

In fact the essence of the meditation is to attain effortlessness and thorough understanding that the mind along with the jeevabhava is just a phenomenon where there is no place for the little ‘i’ to exist as an entity and it disappears to the same abode where the light of the bulb goes when it is off or fused.