I get this question alot but never from somone with a clean mouth. A Chrisitan who asks this question has in my experience, always been somone you does used bad language and is trying to justify it. The Bible speaks volumes about how we should speak and obviously condems cursing and sweating as being sinful. My point in ministry has always been to encourage people to look into their hear. It does not matter if you cuss or if your mouth is clean, the heart is what matters.
A good man out of the good treasure of his heart brings forth good; and an evil man out of the evil treasure of his heart brings forth evil. For out of the abundance of the heart his mouth speaks.
If your heart is soft, dedicated to God and loving to others, filthy or harsh words wont come out of your mouth.
Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry. Because of these things the wrath of God is coming upon the sons of disobedience, in which you yourselves once walked when you lived in them. But now you yourselves are to put off all these: anger, wrath, malice, blasphemy, filthy language out of your mouth.
Angy speech, hateful speech, mocking of God, and all filthy language is not the nature of a believer.
Let the word of Christ dwell in you richly in all wisdom, teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord. And whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks to God the Father through Him.
And whatever you do, do it heartily, as to the Lord and not to men,
Everything you do is for the Lord.
Would you talk to Jesus with fowl language? Would Jesus talk to you that way? Did Paul, Peter, Job, Abraham, or any people of faith in the Bible talk with bad language to God?
Let your speech always be with grace, seasoned with salt, that you may know how you ought to answer each one.
in all things showing yourself to be a pattern of good works; in doctrine showing integrity, reverence, incorruptibility, sound speech that cannot be condemned, that one who is an opponent may be ashamed, having nothing evil to say of you.