Lest there be among you [someone with] a root that will produce bitter herbs (Deuteronomy 29:17).
A person who is diagnosed with, God forbid, a cancer, will submit to that treatment which has the highest degree of certainty of cure. If surgery promises a 50% chance, but the likelihood of cure increases to 70% with the addition of radiation and up to 85% with chemotherapy, a reasonable person will submit to all three treatments, in order to maximize his or her chances of survival. People also know that just removing most of the malignant cells is inadequate, because a single surviving cancerous cell can reproduce itself and be lethal. Furthermore, a malignant growth does not remain localized, but can spread beyond its place of origin to other vital organs.
This approach is also how we must deal with those character traits that endanger our spiritual life. Greed, envy, hatred, selfishness, vanity, and arrogance are all negative traits which must be totally eliminated. Allowing even the smallest remnant of any of these traits to remain is like harboring a single cancerous cell. If we value our spiritual life as much as we do our physical life, we will do everything possible to attain total elimination of negative traits.
Moses speaks of the "root" that will multiply and bear bitter fruit. Any negative trait will not only reproduce itself but, like a malignant cancer cell, may spread and affect other components of one's character.
If we value spiritual life, we will do whatever is necessary to preserve it.