Just do it!
James is saying to us, as you are slow to anger and to speak, carry that out in your daily living by laying aside all filthiness (rhuparı́a: dirtiness as contrasted to cleanliness) and the overflow of wickedness (kakı́a: evil or naughtiness). In short, our words and outbursts of anger reveal the true person within us. As we become more and more possessed by the Holy Spirit, we will increasingly enjoy not the overflow of filth, but rather the fruit of the Spirit of love, joy, peace, longsuffering, kindness, goodness, faithfulness, gentleness, and self-control (Gal. 5:22–23).