How to overcome long-held bitterness — pray for the person consistently; blessing them changes your own heart

Practical counsel from personal experience: the moment any bitterness is detected — a bitter thought, a one-sided mental conversation about someone — pray for that person immediately. Not about them but for them. Ask God to bless them, save them, help their family. Pray for genuine good in their life. Done consistently, this has the effect of dissolving bitterness. Basis: "bless those who curse you, pray for those who spitefully use you" (Matt 5:44 / Luke 6:28). Shame over sin is meant to be temporary; the cross lifts it. The application here is to bitterness toward others rather than shame toward oneself, but the principle of bringing things to the cross applies.