Sin

In Genesis 4, God had an interesting discussion about worship. Cain brought an offering to God and Abel did too. Cain's offering was not a blessing to God and Cain got irritated. A response like Cain's defeats the whole purpose of showing God how much one loves and reveres Him. God addressed the issue at hand:

5 But unto Cain and to his offering he had not respect. And Cain was very wroth, and his countenance fell. 6 And the Lord said unto Cain, Why art thou wroth? and why is thy countenance fallen? 7 If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him. Genesis 4:5-7

God asked Cain why he was downcast and mad.  It was a logical question. If the whole reason for an 'offering' is to show appreciation for God, why would Cain explode about this. God said 'sin' (actually the first use of the word 'sin') is lying at the door. There is indication that the (namely Eve) believed Cain was the man from the Lord.  Could Cain have developed some religious pride about this and thought he was something he was not? The whole thing humiliated him and he was angry. God lovingly explained to Cain that evil repercussions were around the corner and he would need to get a handle on dealing with his heart. Cain didn't do that, but allowed pride and jealousy to get the worst of him.

Focusing on God and doing things out of gratefulness for all he has done for us keeps us out of the soup. That means rethinking through something that is less than the best. Certainly a 'very wroth' attitude does not fit. It is an attitude that needed to be 'ruled' over. Cain rejected God's loving advice and turned another direction which ended up ruining his life.