Taming the tongue may well be the greatest single challenge of Christendom!
But remember, Jesus said, “from the abundance of the heart, the mouth speaks.” {Luke 6:45, Matt 12:34}
Thus, taming the tongue is a matter of first taming “the abundance of the heart”.
The life of continual prayer changes the heart. The simple prayer, “Lord Jesus, Son of God, have mercy on me, a sinner.”
When our hearts are full of the Grace of God, then our tongues will speak it!