A good reason why Christians ought to guard their speech carefully, especially when it comes to cussing is that cussing trivialises certain realities.
Take ‘damn’ for instance. If you think about it, to damn someone literally means to send someone to hell. There are two issues with this. By your careless language, you trivialise the fact that damnation is a serious consequence of sin, and to hear the word as a Christian can only be accompanied with trembling joy that you have escaped the wrath to come. If you frequently use such language, will you not become insensitive over time to such poignant truths? The second issue is that you dispossess the word of its power to shock the hearer. The person who has heard friends playfully cuss will not easily receive the warning of God that real condemnation hangs over the head of every unrepentant sinner. How can he when every time he has heard the word, he has heard it in a non-personal, non-serious context? Don’t compound his situation by using the word yourself.
The same goes for ‘hell’. Hell is a horrible reality we must contend with. It is final judgment for those who rebel against God. No one goes to hell willingly. They are thrown into the lake of fire. We must not trivialise hell by using it as a cuss word. It is a word that ought to be spoken with solemness, with grief, with much pleading, and accompanied by the merciful news of the cross of Christ. If we carelessly toss the word around, how can anyone take the reality behind the word seriously?
Watch your tongue the next time you want to express exasperation. Your words can be like poison, clouding further the spiritual truths of God, Christ, salvation and judgment, from both yourself and those who hear you.