Karma and Liberation

The following was obtained from here

In verse 2.39, Krishna introduces the word Sankhya.

Aeshaa thae(a)bhihithaa saankhyae, buddhiryogae thvimaam s(h)ruNu
Buddhyaa yukthO yayaa paartha, karmabhandham prahaasyasi - 2.39

This knowledge imparted to you till now, deals with Sankhya. Now you listen to this (following teaching) which deals with Yoga. Endowed with this wisdom, you will give up all the bonds of Karma, Oh Arjuna !

Sankhya is one of the six systems of philosophy pertaining to Hinduism. In Gita, Krishna used that word to indicate self-knowledge. Sankhya and yoga are the theory and practice of religion. They do not come into conflict with each other but complement each other. As Atman is understood, life gets enriched.
Yoga is living the life with abundance. By practising yoga, mind becomes more pure and clarity emerges with regard to the concept of atma. Thus jnana and yoga mutually aid.
So Krishna goes on to explain how to harmonise atma and life.
The person who sinned in the past
And
The person who suffers in the present
are one and the same.
In short, the past sinner is the present sufferer!

According to our scriptures, this is the mind-intellect-equipment (sukshma sarira) in each of us.
Why pursue karma yoga?
The knowledge of karma yoga enables to destroy the bondage of karma.
karmabhandham prahaasyasi
Karma here means dharma-adharma, which means punya-papa, the good and the bad actions that alone bind the individual. So it is called the bondage of karma. But this bondage is destroyed by the knowledge made possible by karma-yoga.
Knowledge destroys ignorance and with that, doesrship is destroyed, causing all karmas to fall apart.
To achieve moksha (liberation) both karma yoga and jnana yoga are necessary. Both life-styles imply knowledge. First, to gain knowledge, we need a properly prepared mind and God's grace.
Swami Chinmayananda's words are very relevant here:
One who lives in perfect equanimity in all conditions must necessarily come to live in a realm of his own away from
The pleasure and pain of intellect
The sobs of success and failure of the mind
The fears of loss and gain in the flesh.
To the degree an individual detaches himself from his own body, mind and intellect, to that degree , his ego is dead and therefore, since the "sufferer" is no longer available, thjere cannot be any more "fruits of action" for him to suffer.
Krishna next goes on to praise karma-yoga.