I figured it is better to write a short post twice a month that a long one twice a year.
So I might start writing posts again, but shorter posts this time. :D
You shall not take the name of the LORD your God in vain, for the Lord will not hold him guiltless who takes His name in vain.
What this commandment is saying, is: Don't misuse God's name.
This included exclaiming "Lord", "God", "Jesus" and their euphemisms; including (but not limited to) "gosh", "geez", and "gee". Also, prefixing these words does not help. ("Oh my [bleep]".)
One more thing:
Cursing may or may not be included under this commandment, but Paul says:
Let no corrupt word proceed out of your mouth, but what is good for necessary edification, that it may impart grace to the hearers.
Saying "damn it" is cursing the object, asking for it to be sent to the lake of fire. "Darn it" is a euphemism of the aforementioned phrase and it is also asking for the object to be damned.
Let me end in the words of James, who is speaking about the tongue;
With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God. Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so.