Arjuna a spiritual traveler from beginning of life wanted to settle matters with Kauravas across the table but Duryodhana was not willing to negotiate. No matter how best the Pandavas tried, Duryodhana was not willing to budge. Result, a full-scale mother of all wars, battle of Mahabharata!
Battle of Mahabharata was no ordinary battle fought between two enemies, two communities or two countries. Battle of Mahabharata was necessitated to re-establish Dharma (righteousness) on mother earth. Under all circumstances Arjuna was supposed to win the war. Dharma had to prevail over evil forces under all circumstances.
After all peace efforts failed Arjuna indulged in deeper contemplation (chintan), dialogue with god. And in the battlefield he suddenly reached pinnacle of spiritual pursuit, state of enlightenment.
The Krishna within finally activated. Allegorically Krishna is soul atman existing in all human beings. Dominated by ego we never cared for promptings of soul atman coming from within. Walking path of truthfulness Arjuna not only gave a patient hearing to the voice of Krishna coming from within, he also followed dictates of Krishna.
In doing so he got his answers. Having become an enlightened one he realized the folly of his earlier decisions of not wanting to fight the enemy and feigning cowardice.
As an enlightened soul mounted with power of Chanakya (the most able administrator in the entire history of mankind) Arjuna finally prepared himself to fight the enemy head-on.
The sermon of Bhagavad Gita from Krishna to Arjuna is purely a spiritual deliberation having nothing to do with religious practices (rituals).
Krishna through Bhagavad Gita emphasized on Arjuna to understand cosmic precepts of life like Arjuna was a spiritual traveler manifesting human body. As a soul atman he just could not attach self to workings of physical body (known as Arjuna) and should follow doctrine of nishkama karma yoga, never attaching self to fruits of karma performed.
Realizing that he was primarily a free spirit and death carried no meaning for him any further, Arjuna finally prepared to indulge in battle of Dharma.
Every single enlightened soul like Mahavira, Gautama Buddha, Jesus Christ and Prophet Mohammed passes such stages in life when we are faced with the dilemma of fighting our own brethren, close relatives and friends. After gaining enlightenment, reaching state of self realization, god realization it becomes easier for enlightened one to take firm decisions in matters of Dharma. Re-establishing of Dharma (righteousness) was no ordinary thing. Normal human beings could never indulgence in such things and only an enlightened one like Arjuna could succeed in re-establishing Dharma (righteousness) against evil forces of adharma (lawlessness).
As per Krishna within, the whole gamut of human life is facilitating journey of soul atman within to reach its cosmic end of life. This becomes possible when indulging in spirituality human beings reached state of enlightenment forever.
The gist of all 700 shlokas verses contained in Bhagavad Gita is, undertaking spiritual journey to emancipate from cycle of birth and death at the earliest.
It is only by indulging in spirituality we realized we were a spirit, a soul and not the manifest physical human body.