Hebrews 12:15
Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled;

Anger, biting words, frustration, and constant negativity can certainly wreck any relationship. The root problem to all this is often bitterness in the heart. Bitterness will often take root in a heart due to a festering wound that has never been healed. Anger, frustration, negativity, and hatefulness are just leaves springing forth but underneath hidden from the eye is a root called bitterness.

"But you don't know how bad they hurt me!" Then why are you allowing them to continue hurting you by staying bitter? God's way for people to gain victory over bitterness is to expose it! The way to deal with a hurt is to uncover the hurt and then apply the appropriate medicine in order to produce healing. Share your heart and hurt with God, ask God to help you forgive those who have hurt you deeply and then let it go.

If let untreated, bitterness will eat you alive! It is an acid on the human heart that slowly eats away at your joy and peace. The root of bitterness will cause you problems in other relationships. Forgiving the offender and letting it go doesn't mean you are excusing them for the hurt nor does it mean you have to allow them to continue hurting you. Forgiving somebody and letting go of the hurt is for more for YOU! Holding on to bitterness is like drinking poison and hoping the other person dies! You are only hurting your self. There are those around you who would love to have a more meaningful relationship with you but are stifled because of bitterness.