There is much in the Book of Proverbs about the mouth.
The most concise passage is probably in the first part of Proverbs 18: 21:
"Death and life are in the power of the tongue . . ."
I have actually had Christians say to me, "I just can't help it. It just comes out before I can stop it!"
You can stop it, but it is a matter of first wanting to have words that line up with His Word, and then wanting to be changed. Being changed is never an overnight process and it is never without some skin-shedding.
The battle does not begin with the tongue, it begins in the mind. There has to be an awareness of what the thoughts are. If the heart flows out of the mouth, it means that the heart is marinated in the thought life.
And, we are told we have the power to control the thought life. We can't always control what comes into the thoughts but we can certainly focus on what is godly and right.
So many are Christianized, but have no regular feeding on the Word of God that is Alive and Full of Power.
This is a life-long matter and critical to every walk of life.
Take it to Him today.
Aloud. Aloud because that prevents wool-gathering, and the Holy Spirit will lead you in your choice of words. It is one of the ways God speaks to us.