A friend told me about a man whose daily speech was so profane that when he talked aloud in his sleep, he swore. After he became a Christian, he began memorizing Scripture, a few verses every week. That didn't stop his nocturnal commentary, but it changed what he said. Instead of swearing, he began quoting the Bible in his sleep. The most effective cuss control takes place when we let God change our hearts.
Clean words come from the well of a clean heart.