Never harbor grudges; they sour your stomach and do no harm to anyone else.

The remark frames resentment as a form of self-inflicted damage: a grudge is pictured as something ingested that “sours” the body, poisoning the grudge-holder rather than the target. The practical moral is that anger preserved for its own sake rarely produces justice or change; it mainly corrodes one’s health, mood, and judgment. By stressing that it “do[es] no harm to anyone else,” the line punctures the common fantasy that private bitterness punishes an offender. The implied counsel is psychological and ethical: release grudges not to excuse wrongdoing, but to refuse ongoing self-harm and reclaim agency over one’s inner life.