Bitterness is a poison that we prepare for someone else but then drink ourselves. It is something we often carefully nurture and grow over the years. If someone hurts us—whether intentionally or unintentionally—and we begin to fantasize of a thousand and one ways to get payback, all we are doing is destroying our own heart and mind. Thankfully, our faith presents a better way to live. Rather than nurture hate, we can “turn from evil and do good; seek peace and pursue it” (Psalm 34:14).
https://intouch.org/read/daily-devotions/a-bitter-poison