Some bitter people are like a porcupine. They may have a lot of good points, but they are hard to be near. They are harsh, critical, judgmental, sarcastic, and filled with anger.
Other bitter people are like an iceberg…very cool, aloof, and politely indifferent. They seem to have a sign on them that reads, “I don’t need anybody.” And like an iceberg, most of their problems are beneath the surface.
Hebrews 12:14 says, “Follow peace with all men, and holiness, without which no man shall see the Lord: 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.”
LWF.org