When a person is rejected, it is more about them as a person, rather than something they have done. This pain is the kind that goes so deeply that at times it feels as though it could split you in half and wash you away and no one likes to be hurt like that! When it happens, our pride gets all uppity and our sinful heart determines, "No one is going to treat me that way!"
This leads to living out the sins Ephesians 4:31 tells us to unload from our hearts!
Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. Ephesians 4:31 (NASB)
When a person responds wrongly it is because the initial anger is not dealt with biblically and that anger turns to bitterness. They become bitter when they come to believe that the one who sinned against them is not sorry and is not going to ask forgiveness. The also become bitter if they believe God is dealing with them unfairly. That bitterness is justified because something has been done to them so they consider it a natural response. (It is a natural response, out of the natural man or sinful heart. Not acceptable for a Christian.)
The truth is the mistreatment was real! Rejection is painful and often is the result of or a part of being mistreated. Often, God is blamed for not intervening in the matter. People become bitter toward God because they believe God will not punish the people who hurt them, God is not hearing their plea, or He does not care about their plight. Since God isn't going to avenge them, they take matters into their own hands.
The thinking becomes circular and the more they dwell on what has been done to them, the injustices they have suffered, or the loss they have incurred, the deeper the root of bitterness goes.
It is important to understand that God allows these circumstances in the lives of His children. He uses all events in our lives to make us more like Christ. Our response to attack and accusations and rejection needs to follow the pattern set forth in Scripture.
So, as those who have been chosen of God, holy and beloved, put on a heart of compassion, kindness, humility, gentleness and patience; bearing with one another, and forgiving each other, whoever has a complaint against anyone; just as the Lord forgave you, so also should you. Beyond all these things put on love, which is the perfect bond of unity. Let the peace of Christ rule in your hearts, to which indeed you were called in one body; and be thankful. Colossians 3:12-15 (NASB)