'Impressions', translated into Sanskrit is samskara, the word in use here. The Sanskrit meaning of this is more versatile. It denotes, up bringing, enculturation, education, etc., which leave indelible impressions in our mind and psyche and shape our character, future actions and thoughts. Samskara also means to purify, to enrich tendencies, potentialities etc. There are many samskara rituals recommended in the Vedas for erasing bad samskaras and replacing them with good ones. Thus having purified the consciousness from mundane contamination, these impressions become our lifelong companions. There are many impressions we carry with us from our previous incarnations, what Western psychology refers to as 'hereditary' tendencies. This can be explained in this manner that our karma makes us choose a certain family where we 'inherit' tendencies etc. instilled in us in that family. A mind bereft of proper samskara and left to its own designs will constantly draw our attention to the world of phenomena and the inconsequential and yet disregard the immeasurable value of the human birth and the momentous task of its emancipation from the grip of illusion and suffering.
Citta in its original state is pure spiritual consciousness, transcendental and pervaded by Absolute Reality and unlimited bliss. But when it comes in contact with matter and the physical body, it becomes temporarily contaminated by the influences of duality and illusion. This gives rise to delusion, making us confounded about the nature of the material world and one's real identity. The practice of yoga initiates the process of inner purification, of the citta. In other words, yoga practice creates new samskara. The Sage Patanjali exhorts us to understand the priceless value of a human birth. The Vedas declare that after millions of birth in other species [There are exactly eighty-four million] the rare human birth is attained. Only when someone understands that liberation from the cycle of repeated birth and death is possible to attain in the human form alone and in no other, does he/she become serious about the knowledge of atman and Paramatman. On the other hand, many may have to wait even a lifetime before they can begin this process due to lack of gumption, knowledge and determination. Or, simply because of not having the good fortune of having the possibility to come in contact with this knowledge. The spiritual spark, which Vedas refer to as atman, possesses certain intrinsic qualities like, eternal existence, transcendental knowledge, spiritual bliss and free will to a limited degree.