As per Lord Krishna in Bhagavad Gita the present journey of life belongs to atman, spirit existing in our heart. It is this atman, consciousness within that manifested human form to work out its karma, remove dross impurities within.
Existence of atman is central to existence of life in cosmic system. As no atman can purify itself of its own, it needs a medium a body to reach state of absolute purity forever. When human beings indulging in Bhagavad Gita, spirituality finally reached state of enlightenment, it announces the atman within regaining its lost original pure prime pristine primordial form.
Bhagavad Gita is all about inner journey, a journey towards atman existing in our heart.
Ever since Brahman, God Almighty exploded self with a big bang all souls’ atmans that were pure in form scattered all over cosmos at unimaginable speeds. In the melee, hurtling souls’ atmans in their cosmic sojourn gathered impurities similar as a rolling ball gathers moss.
No sooner life supporting planets like mother earth evolved in cosmic system, hurtling atmans immediately manifested a body on mother earth. And thus starts cyclic life cycle of a soul atman. Body after body, manifestation after manifestation this journey of atman on mother earth continues until it reaches state of absolute purity. In absence of dross impurities within the pure soul atman need not manifest a human body again.
The human form is but a medium for atman within to reach state of absolute purity.
Doctrine of karma, law of karma is central to evolution in cosmic life cycle. In absence of karma, life simply would not move ahead in cosmos, everything would decay and die. It is karma that facilitates residual balance of past life to next manifestation. Whether we manifest a form in the house of a laborer or a king is solely dependent on residual balance of karma of previous life.
The most important precepts of spirituality to be followed by human beings are demolition of ego in totality and overpowering five senses and mind. To overpower five senses and mind karma has to be negated to zero, only then human beings can emancipate from cycle of birth and death forever. What fun rotating in endless cycles of birth and death again and again?