Sticky Note:  "Good" people need Jesus.

Conflict exposes what is in our hearts, and "good" people find out they are big sinners who need a big Savior.

Cain's offering was not accepted because he felt God owed him divine favor for the offering he brought.  This offering is not offered in faith.  

The one who offers in faith knows that it doesn't deserve God's favor, but delights to receive that favor as a gift by faith.

The Father's face was turned away from Jesus on the cross (what WE deserve) so that the Father's face would always be turned toward us (what Jesus deserves).