Get rid of all bitterness, rage and anger, brawling and slander, along with every form of malice. - Ephesians 4:31
Bitterness is something we feel never will happen to us. We go through life opening our hearts to many people, seeking friendship in this life. But when we least expect it someone hurts us, or circumstances themselves come to a place where we allow bitterness to come into our hearts towards even God himself. Feeling angry and disappointed over how we have been treated or how circumstances have treated us produce great bitterness in our being. This feeling we hold in is suppressed in our hearts and not see at first in our daily life. But it starts to seep out its poison slowly in our words (James 3:7), and mind, we start to judge everyone, say cynical and hard comments towards others. Usually this hurt is directed towards a person or specific situation. Anything that would remind the hurt person of this situation will result in their hurt to come out in words that damage and tear down others.
In the verse before this passage the Apostle Paul speaks of not grieving the Holy Spirit as believers in Jesus. He shares that Disciples must "get rid" of all of these hurt feelings that result in resentment, anger, frustration, hurtful words towards other persons. If we allow any unforgiveness as believers to rest in our hearts it will grow like a cancer and create bitterness and then our inner man is defiled with all these sins of anger. The Apostle pleads with fellow believers to forgive "each other, just as in Christ God forgave you." (Ephesians 4:32). That is the only solution and way to solve the problem. Getting even, hurting someone else or an organization will not result in releasing you from the personal prison of bitterness you are in. Forgiveness is the key that will open that door so that you may walk in the freedom Christ has called you in and then you will be able to help release others who even caused the hurt in your own life.