Angry?

If you are an angry person - getting angry easily or staying angry once you're there, then watch out. Sin is right at your doorstep.

Abel brought fat portions from some of the firstborn of his flock. The LORD looked with favor on Abel and his offering, 5 but on Cain and his offering he did not look with favor. So Cain was very angry, and his face was downcast.
6 Then the LORD said to Cain, "Why are you angry? Why is your face downcast? 7 If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must master it."
8 Now Cain said to his brother Abel, "Let's go out to the field." And while they were in the field, Cain attacked his brother Abel and killed him.

Genesis 4:4-8

Cain got angry, and worse, he stayed angry. His anger led him to to take it out on his brother Abel, who hadn't done anything to him. God had warned Cain "sin is crouching at your door" - in other words "you are very close to sinning." Cain should have repented from his attitudes and actions that displeased God (not bringing the type of offering God had requested). He wanted to serve God his way and expected God to accept him. But God demands that we worship Him HIS WAY.

Yet instead of repenting, Cain let his anger get the better of his mind and heart. He blamed his brother for his poor relationship with God or envied him for having a better relationship with God. Either way Cain lashed out at Abel and killed him.

Unchecked anger twists our mind and leads to destructive and sinful actions. Which is why the Bible tells us that 26"In your anger do not sin": Do not let the sun go down while you are still angry, 27and do not give the devil a foothold. (Eph. 4:26-27) When we stay angry and don't deal with it quickly we allow the devil a beachhead within our hearts from which to launch attacks and get us to sin against God and others.