We think of "foul language" as "swearing". It can be but "foul language" can be anything that isn't helpful or positive. As with most things in life, our words can fall into three categories: Positive, Negative and Neutral. "If you don't have anything nice to say (negative), don't say anything at all (neutral)". But why don't we actually put some effort into life and be kind, grateful, thankful and loving (positive) with our words toward others.
Lord, help my words to be encouraging and kind and not absent or hurtful.