Unforgiveness becomes the mortar by which the bricks of bitterness are held together. Bitterness is the root that defiles the pure work of God. Defilement leads to decay and destruction.
The path of bitterness takes a long time to retrace once you have gone down it. Bitterness is a rottenness in your soul that gnaws and nags, it slowly festers in your heart. Bitterness is a rotten root, and when it springs up, it shows itself in short temper, sour disposition, judgmentalism and depression. Bitter people are lonely people, because nobody wants to be around them, except others also nurturing bitterness. They drag one another down and feed the bitterness by grumbling and complaining. The isolation from more positive people just creates more bitterness. The spiral is not a good one.
Bitterness is much like a garden that needs tending.. As you clear the garden and strive to keep it clear, it became obvious that it is much easier to pull the weeds before the roots spread themselves and grow deep. Once they have dug in, you can no longer just pull them, but have to get the shovel to make sure you get all the roots out. The same is true with bitterness. The longer you let it grow, the tougher the root will become, and the harder to get it out of your soul. Look out for those weeds of bitterness. Clean out their influence by offering them up to God.