why are we here?

Q. By what is one impelled to sinful acts, even unwillingly, as if engaged by force?

A. Krishna was categorical in His answer to the above question. He said

śrī-bhagavān uvāca
kāma eṣa krodha eṣa
rajo-guṇa-samudbhavaḥ
mahāśano mahā-pāpmā
viddhy enam iha vairiṇam

It is lust only, Arjuna, which is born of contact with the material mode of passion and later transformed into wrath, and which is the all-devouring sinful enemy of this world” (BG 3.37)

The soul or the living entity is the marginal energy of the Lord. It is in a position where it can come in contact with the inferior material energy or superior spiritual energy. When it is in contact with the spiritual energy, it is called Krishna consciousness. But when it is in contact with the inferior energy, it becomes material consciousness. This contact with material energy is due to lust that has been transformed from love for Krishna. Since lust is never satiated, the living entities are always bewildered by maya. Since unfulfilled lust can turn into anger, illusion and ultimately bewilderment of memory perpetuating the living entities stay in the material world; it (lust) is considered the greatest enemy of the living entity (BG 3.37)

A scientific explanation of the work of lust has been presented nicely in BG 3.40. Mind is the center of all activities of the senses. In other words, with our mind we contemplate the sense objects using our senses. Therefore the mind is superior to the senses in that we use our mind to control the activities of the senses and sense objects. Intelligence is superior to the mind as it can control the mind in telling right from wrong. Since the intelligence is filled with lust to lord over material nature, the soul is influenced from time immemorial by this lusty intelligence and hence acquires a false ego which is superior to intelligence. Therefore the soul which is spiritual is superior to intelligence, mind and senses which are material. However, due to lust, the soul falls down from its spiritual position and associates with matter thinking matter to be the self. This lust alone is the cause of our downfall and hence considered the number one enemy of the living entity (the soul).

Srila Prabhupada explains in BG 3.41

āvṛtaḿ jñānam etena
jñānino nitya-vairiṇā
kāma-rūpeṇa kaunteya
duṣpūreṇānalena ca

Thus the wise living entity's pure consciousness becomes covered by his eternal enemy in the form of lust, which is never satisfied and which burns like fire.

that lust is but a perverted reflection of our love of God. Therefore simply by employing our lust for Krishna unconditionally and unmotivated, our lust actually becomes love for Krishna and this is Krishna consciousness in the pure stage. We start our process of Krishna consciousness by regulative principles (in the initial stages) and slowly progressing in the ladder of bhakti, we can achieve suddha bhaki or prema to Krishna.

Concluding, to know one SELF (the soul) to be transcendental to all the mundane elements such as the mind, intelligence and the senses, we practice devotional service in a steady and regulative manner, thus, ultimately conquering lust and attaining pure love of Krishna.