The robbers are in the Veda vital beings who come to steal away the good condition or else to steal the gains of the sadhana.
There is and can be no psychic being in a non-evolutionary creatures like the Asura; there can be none in a god who does not need for his existence. But what the god has is a Purusha and a Prakriti or Energy of nature of that Purusha. If any being of the typal worlds wants to evolve, he has to come down to earth and take a human body and accept to share in the evolution. It is because they do not want to do this that the vital beings try to possess men so that they may enjoy the materialities of physical life without having the burden of the evolution or the process of conversion in which it culminates.
Some of the vital beings are very intelligent but they do not make friends with the Light — they only try to avoid destruction and wait for their time.
The depression came into you subconsciously because you had the discussion with X. When you discuss like that with people, you put something in them, but something also comes from them to you. In speaking with others there should be always be a sort of instinctive defence, except with those who are free from the ordinary vital impulse.