Arjuna in Bhagavad Gita represents a seeker in search of God about to realize him but simultaneously he is also fighting his arch enemy Kauravas that consisted of his close cousins, relatives and friends even his maternal grandfather Bhishma Pitamah and Guru Dronacharya.
As long as Arjuna considered self an instrument of circumstances, he was not willing to fight his arch enemy Kauravas because they consisted of many people closely known and related to him. But finally spirituality prevailed and Arjuna realized from within that he was primarily a spirit, a cosmic traveler that manifested physical form of Arjuna.
As Arjuna had succeeded in reaching state of enlightenment in the battlefield, he finally realized that all earthly ties meant nothing to him any further. Only after cutting all earthly ties, bondages he had succeeded in reaching state of enlightenment and in the circumstances he also realized that apart from being a Pandava Prince he was also the chieftain of the army and also his countrymen. For the sake of millions of countrymen and soldiers he had to fight.
Furthermore the battle of Mahabharata was a battle of Dharma to re-establish Dharma (righteousness) at all costs. Under no circumstance of life can Arjuna ever sway from that. The voice coming from within his heart was Lord Krishna talking to him all the time. Metaphorically Lord Krishna represents our soul atman, the spiritual traveler existing in our heart all the time. It is this spirit, Prana energy that manifests physical human form.
Once the cosmic truth dawned upon Arjuna he finally prepared himself to fight the enemy head-on. Thereafter it was no looking back and Arjuna not only succeeded in winning the battle but also re-establishing dharma (righteousness) defeating the evil forces of adharma (lawlessness) head-on.
Here one thing needs to be observed. For an enlightened one fighting the enemy is very surprising. Mahavira, Gautama Buddha even Jesus Christ and Prophet Mohammed after reaching state of enlightenment could not even think of indulging in anything physical.
On path of pure spirituality there were three sides of the earthly story. After gaining enlightenment one some enlightened souls immediately left the mortal frame and attained moksha salvation. This happened in case of Gautama Buddha who gained enlightenment 80 years of age and left his mortal frame at 81.
Mahavira (24th Tirthankara of Jainism) gained enlightenment 42 years of age and for full 30 years he indulged in deshna (spiritual discourses) to give back to the society whatever he gained on spiritual path.
In the third circumstance the enlightened one takes upon self the responsibility of re-establishing dharma (righteousness) and this is what Arjuna did. Such an enlightened one practically is a lethal combination of an enlightened one plus Chanakya (the most able administrator in the entire history of mankind). To save lives of millions of soldiers and countrymen Chanakya got 100 kings eliminated in one night. Kings unaware of their surroundings, drenched in ill doings and fighting their neighbor kings all the time.
Amongst all the three cases of enlightenment, the character of Arjuna reigns on the top.