"[I]f you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it." -Genesis 4:7 (NIV)
[Cain even copped an attitude with God: "Am I my brother's keeper?"]
Sin isn't something to be excused away. It's to be ruled over. Jesus defeated sin for us on the cross!! And only Jesus in us, through the power of His Spirit, through the power of His Word, can slam the door to sin.