Bhagwad Gita - Post 239

Verse 58

Fixing thy mind on Me, thou shalt by My Grace overcome all obstacles; but if from egoism thou wilt not hear Me, thou shalt perish.

Having advised Arjuna what to do in the previous verse, Sri Krishna now declares the benefits of following his advice and the repercussions of not following it. 

The soul should not think that it is in any way independent of God. If we take full shelter of the Lord, with the mind fixed upon him, then by His Grace all obstacles and difficulties will be resolved. 

But if, out of vanity, we disregard the instructions, thinking we know better than the eternal wisdom of God and the scriptures, we will fail to attain the goal of human life, for there is no one superior to God, nor is there any advice better than His.

  

Verse 59

If, filled with egoism, thou thinkest: “I will not fight”, vain is this, thy resolve; Nature will compel thee.

Right at the beginning of the Mahabharatha war, when Arjuna asked Sri Krishna whether to fight or not, Sri Krishna could have given the answer right away. But He decided to deliver the discourse of the Gita instead, not just for Arjuna’s benefit but for the benefit of all future seekers. 

Having done so, he now vehemently points out the flaw in Arjuna’s decision. He says, in crystal clear language, that the decision to not fight is wrong. It is purely ego-driven, and not in line with Arjuna’s duty as a warrior.
 
In our personal experience, we come across stories of children who were misfits in their families and communities simply because their prakriti, their nature, their samskaaraas, were completely different. 
 
Parents have a strong sense of mine-ness with regard to their children. They prefer not to think of their children as independent entities. 

Similarly, Arjuna also assumed that he could override his nature as a warrior, and become a monk. Sri Krishna reminded him that his inherent nature as a warrior would compel him to fight, and that he should reconsider his decision.

At the highest level, this verse should be understood in this way,

“Our inherent nature being divinity, even if we undertake actions out of ego and ignore the inner divinity, ultimately, a stage comes in each and every one’s life when he/she turns towards God/ SELF and undertakes sadhana so as to act/think/ exist as per one’s real nature - DIVINE SELF”

Love.