"If you do well, will not your countenance be lifted up? And if you do not do well, sin is crouching at the door; and its desire is for you but you must master it."- Genesis 4:7 (God speaking to Cain before he kills Abel)
In this verse God is speaking to Cain concerning the offering he gave to God that God did not accept. I find it interesting that God tells him "do well", he doesn't tell him how to do it - no secret formulas to "Becoming a better Cain" or "Living His Best Life Now!". God simply tells him to do well. It leads me to believe that God has already implanted with in Cain's heart, as well as all of humanity’s heart, the way to do well, all Cain has to do is: do well.
The hard part is what God says right after that though "...sin is crouching at the door; and its desire is for you but you must master it." (Mastering sin - what a crazy thought.) In a novel by John Steinbeck "East of Eden" this same idea was contemplated by the author - in the book one man goes for months studying this one verse in the original Hebrew with elders in his community and they decided that the best interpretation for the verse was that God said "thou mayest master it[sin]" instead "thou must", giving Cain the option to not master it and let it take over his life. As we all know Cain did not master it and went out a killed his brother Abel. Lucky for us God doesn't give us the same choice, because He sent Jesus to master sin for us. "He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him." (2 Corinthians 5:21)
The craziest thing is that God seems to always be giving humanity, as whole, choices and with sin He has said: "thou mayest master it" or basically let it master you. I think the choice we made was the latter. Instead of stopping the gross sins of greed; we allow our governments to make it easy for greedy corporations to destroy our world while overcharging us for the service. Instead of stopping disgusting sexual immorality, the pornography industry capitalizes on people's perverted fetishes making it one of the most profitable industries - making an estimated 10 Billion dollars a year according to a CBS report. Why should continue to allow ourselves to be mastered by sin, when Christ has paved a way for us to walk in spiritual freedom?
I find that there are universal morals - we all know not to murder, not to steal, or lie, cheat, etc. And I know there are some gray areas where even scripture seems to go both ways, but for the most part we all know how to "do well", so I say let's do it! Instead continuing to allow sin to master us, let us show sin that we have a new master, the King of kings and Lord of lords.