Why Should One Follow the Path of Dharma?

In Mahabharat, Karna asks Lord Krishna - "Oh Krishna, My mother left me the moment I was born. Is it my fault I was born an illegitimate child? I did not get the education from Dhronacharya because I was considered not a Kshatriya. Parsuraam taught me but then gave me the curse to forget everything when he came to know I was Son of Kunthi belong to Kshatriya. A cow was accidentally hit by my arrow and its owner cursed me for no fault of mine.I was disgraced in Draupadi's Swayamvar.Even Kunthi finally told me the truth only to save her other sons. Whatever I received was through Duryodhana's charity. So how am I wrong in taking his side ???" 

Lord Krishna replies, "Karna, I was born in a jail. Death was waiting for me even before my birth. The night I was born I was separated from my birth parents. From childhood, you grew up hearing the noise of swords, chariots, horses, bow, and arrows. I got only cow herd's shed, dung, and multiple attempts on my life even before I could walk! No Army, No Education. I could hear people saying I am the reason for all their problems. When all of you were being appreciated for your valour by your teachers I had not even received any education. I joined Gurukula of Rishi Sandipani only at the age of 16! You are married to a girl of your choice. I didn't get the girl I loved & rather ended up marrying those who wanted me or the ones I rescued from demons. I had to move my whole community from the banks of Yamuna to far off Sea shore to save them from Jarasandh. I was called a coward for running away!! If Duryodhana wins the war you will get a lot of credit. What do I get if Dharmaraja wins the war? Only the blame for the war and all related problems... Remember one thing, Karna. Everybody has Challenges in life to face. LIFE IS NOT FAIR & EASY ON ANYBODY!!! But what is Right (Dharma) is known to your Mind (conscience). No matter how much unfairness we got, how many times we were Disgraced, how many times we Fall, what is important is how you REACTED at that time. Life's unfairness does not give you license to walk the wrong path... Always remember, Life may be tough at few points, but DESTINY is not created by the SHOES we wear but by the STEPS we take.