The Lord accepted Abel and his offering, 5 but he did not accept Cain and his offering. This made Cain very angry and dejected. 6 "Why are you so angry?" the Lord asked him. "Why do you look so dejected? 7 You will be accepted if you respond in the right way. But if you refuse to respond correctly, then watch out! Sin is waiting to attack and destroy you, and you must subdue it."
I cannot remember who the pastor was that said this but he said that that the term "dejected" in this passage is better translated that Cain was out of control with fury.
There was nothing wrong with Cain's offering, rather it was his attitude that was wrong. He had issues within himself and this was shown with his fury which caused him to sin.
Although all of our sins are forgiven though Jesus, we still need to continually grow spirtuatlly. If we are reacting to anything with anger or fury we really should be looking deeper into ourselves to determine the issue. With God's help and the power of the Holy Spirit we can overcome anything standing in our way of spiritual growth.
Lord, please help me to deal with those moments of anger. Please give me the patience I need and the wisdom to create better situations. In Jesus Name. Amen!