"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 NASB)
Most people know that Cain killed Abel. He was basically jealous of his brother's favor. Cain didn't offer God a worthy sacrifice; he should have repented and corrected the error. Instead, he was angry with Abel and killed him. God warned Cain that sin was waiting to trip him up, but he fell into the trap anyway.
How many of us continue to go down paths that we know won't end well? How often do we just give in to our fleshly desires? If God said to Cain "but you must master it", then it must be possible to overcome our sinful nature. We can't blame anyone else for our shortcomings. We need to own up to our faults, confess them to the Lord, and ask for His help.
We must exercise self-control, which just so happens to be a fruit of the Spirit (Galatians 5). With God's spirit living inside us, we can not only offer an acceptable sacrifice, but we can interact with one another in love. We must conquer sinful urges through the power of the Holy Spirit. You can master it!