In the Scripture bitterness is almost always connected with suffering. It is a sign of not suffering well. Great suffering lead Naomi to declare rename herself Mara (Bitter).
Bitterness is called a "poisonous root." Another reality the Scripture shows us is that bitterness leads to self-reliance. The author of the Hebrews pairs together the root of bitterness with the rebellion of Esau.
See to it that no one fails to obtain the grace of God; that no “root of bitterness” springs up and causes trouble, and by it many become defiled; that no one is sexually immoral or unholy like Esau, who sold his birthright for a single meal. For you know that afterward, when he desired to inherit the blessing, he was rejected, for he found no chance to repent, though he sought it with tears. - Hebrews 12:15-17
But, it doesn't stop there. Bitterness has effects on this around us as well. Proverbs 14:10 talks about others not sharing in the heart's joys due to bitterness. Hebrews warns of it defiling "many." Moses warned the congregation of Israel to avoid it (Deut. 29:18-19).
God's answer to those caught in the tangle of the poisonous root? Christ is the Gardener!
“I am the true vine, and my Father is the vinedresser. Every branch in me that does not bear fruit he takes away, and every branch that does bear fruit he prunes, that it may bear more fruit. - John 15:1-2
First, bitterness may be rooted suffering, but suffering may also be it's cure. Pruning is not a pleasant process, but Jesus promises to prune us so that we might produce fruit. All of our suffering is working to conform us into the image of Jesus. In fact, according to Romans 8:28-30, all things are.
Second, bitterness is a worship problem. Over and over the Bible points the bitter, through Christ, to worship the Lord.
But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, and to innumerable angels in festal gathering, and to the assembly of the firstborn who are enrolled in heaven, and to God, the judge of all, and to the spirits of the righteous made perfect, and to Jesus, the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel... Therefore let us be grateful for receiving a kingdom that cannot be shaken, and thus let us offer to God acceptable worship, with reverence and awe, for our God is a consuming fire.
- Hebrews 12:23-25, 28-29
Third, bitterness is a forgiveness problem. We are called to forgive as God has forgiven us. This requires a proper recognition of our condition and Christ's kindness.
The cross and Resurrection is the greatest example of kindness mankind has ever experienced.
Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you. - Ephesians 4:31-32
Kindness softens the bitter heart. Paul writes that the "kindness of God leads us to repentance" (Romans 2:4-5).
Fourth, bitterness has bitter results. We are warned that those who persist in bitterness are met with separation from God! Recall Moses warning to the Israelites,
Beware lest there be among you a root bearing poisonous and bitter fruit...The Lord will not be willing to forgive him, but rather the anger of the Lord and his jealousy will smoke against that man, and the curses written in this book will settle upon him, and the Lord will blot out his name from under heaven. - Deut. 29:18, 20
Bitterness has been a besetting sin in my life for the past 2 years or so.
But, in God's kindness, He is breaking the hold of bitterness on me. One day at a time.
This breaking involves repentance. I repent to all who are reading this of my bitterness. First and foremost, my repentance is toward God (Psalm 51), but I also recognize that healing comes from confessing out sins to one another (James 5:13-18). I come to say I'm sorry. I come to find healing.
Pray for me in these things. That God would continue to break me and that I would keep my eyes on his kindness toward me. Psalm 130:7 describes the kindness of the Lord this way,
"For with the Lord there is steadfast love, and with him is plentiful redemption."
That kind of kindness shatters the hold of bitterness. Praise God.