Our speech and conversation is one aspect of our behavior that tells others what kind of person we are. Speech also betrays what we think about, because our thoughts lead to our words.
If we feel the need to correct our language, whether it be profanity, evil speaking, omitting praise and gratitude, or other similar corrections, we should first focus on our thoughts. Controlling our speech in spite of what we think about is a difficult venture, and will never correct the root problem.
Thoughts can be controlled. Rather than entertaining any thought that enters our minds, we should systematically sort through the bad and focus on what is best.