If any man among you seem to be religious, and bridleth not his tongue, but deceiveth his own heart, this man’s religion is vain (empty).       James 1:26

The issue here is not changing one’s speech.  A person can change his/her speech for the better and still die and go to hell.

The issue is the heart.  Jesus said that we speak out of the abundance of the heart.  He said that it is not what goes into a man that defiles him, but what comes out of the mouth.

Jeremiah declared: The heart is deceitful above all things, and desperately wicked: who can know it?  Jeremiah 17:9

The tongue reveals the condition of the heart.  It is the heart that needs to be changed.

A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.  Ezekiel 36:26

A changed heart makes a new creature.

Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.                                                II Corinthians 5:17

For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.  John 3:16

…….Consider it to be so……