When the day came to make an offering to God, Cain and Abel brought their tribute. Abel brought some of the very finest from his flocks, while Cain deliberately brought an average-quality offering from his crops. Cain could have done better, but he chose not to for some reason. Perhaps he thought that the all-knowing God would not notice.
God accepted Abel's offering with favor, but He rejected Cain's offering. It wasn't due to a preference of meat over vegetables, but rather that Abel had brought the best that he possibly could, and had done it willingly. Cain knowingly brought not his best, and even then brought it grudgingly. The very same offering would have been accepted if it had been the best that he could do, and if he had offered it with the right attitude. Abel was cooperative and generous; Cain was selfish and miserly.
Even though the rejection was his own fault, the incident made Cain very jealous and angry with Abel, entirely without cause. Abel had merely done what God expected of him. The rest of the tragedy is well known. Cain allowed his jealousy to turn to anger, and then his anger to hate. Instead of bringing himself up by doing better next time (as God plainly explained to him in Genesis 4:7), he chose to take Abel down - he committed the premeditated murder of his own righteous brother.
Abel is described as "righteous" in the New Testament. He didn't live very long in this life, but he will more than make up for it in the next. With whatever he had to work with, he had simply made his best possible effort - exactly what God expects of us today.
My response - When you feel yourself slipping into darkness, just know that he's always there with you, keep praying on what you should be doing in your daily walk. I think that Cain lacked faith and committed the sin of sloth. At the end of the day it's our choice to live in the light or the darkness.
Have Faith and Trust in the Lord - Yah1 Romans 8:26