Many people understood karma as law of cause and effect. This is an absolute misnomer, only one part of the entire story. On the physical plane karma definitely is a law of cause and effect. But on spiritual scale law of karma has a very deep-rooted meaning.
As per Hinduism we are primarily a spirit, a spiritual traveler on its cosmic life cycle. As a soul atman we manifest human form to cleanse self of dross impurities within. This cleansing of soul atman becomes possible only when the physical manifest form indulged in karma.
Without indulgence in karma no life on mother earth could evolve. For human beings to grow from within our indulgence in nishkama karma yoga is necessitated. The doctrine of nishkama karma yoga simply means offering fruits of karma performed to God Almighty all the time.
In spiritual terminology every inch of karma indulged by human beings precipitated fruits of karma. As the human body is manifested by soul atman within, fruits of karma indulged by human beings always belonged to soul atman within and never the manifest physical human form.
As souls’ atmans were in essence God Almighty himself in miniscule form, fruits of karma either belonged to soul atman or God Almighty himself.
On the physical scale the law of cause and effect simply means as we indulged accordingly shaped our destiny. Law of karma means as we sow so shall we reap nothing less or more. We just cannot expect mangoes to grow on a guava tree.
Our present always results from karma indulged by us in past. At no stage of life anything is governed by God Almighty himself. It is always karma that rules the roost. We just cannot blame God Almighty for of sufferings, woes. Everything results from karma indulged by us in past.