When I was a child, I was told repeatedly not to "take the lord's name in vain." I do not recall anyone ever taking the time to explain why this was so important (other than pointing to our "holy" book) or even what it meant; all I knew was that there were certain words I was not supposed to utter. One of the first words to escape my mouth in this context was "goddamn." It was a common expression of anger, frustration, or surprise (depending on the inflection) that I heard fairly often. I heard it from my dad, from other children in school, and from other adults (who were often apologetic about it afterward). At the time, I hadn't given much thought to what it meant. I repeated it because I had learned that it was a word one used in certain situations.
When I said "goddamn," the reactions I received were variable. If it was delivered in an appropriate context (e.g., right after hitting my thumb with a hammer), my dad would usually ignore it or say something like, "Just don't let your mother hear you say that." My mom would usually be the one to warn me about "the lord," but even she would sometimes give me a pass if the circumstances seemed to justify the word. Public school was another matter. They didn't care about taking anybody's name in vain, but I'd be disciplined for using the word in any context.
I can easily contrast "goddamn" with another "bad word" for which I received much more consistent reactions: "fuck." If that word slipped out of my mouth at home or school, I was going to catch hell for it. It was a word I didn't hear often at home, as it seemed to be reserved for the most extreme situations (e.g., a lug nut rolling under the car while my dad was changing a tire). While I did hear it at school, my classmates were careful about not using it in front of teachers. I learned quickly that this was a word that would bring swift and unpleasant consequences that had little to do with any lords.
And then there was the most fantastic word of all, not even a word but a name: "Jesus Christ." For the life of me, I couldn't figure out why it was perfectly acceptable for the minister to repeatedly say "Jesus Christ" throughout his sermon and I'd get scolded for using it in place of "goddamn." It was the name of someone I was supposed to worship, but I wasn't supposed to use it. Eventually, I'd figure out that it came down to how I used it as to whether it was acceptable or not. But it still didn't make much sense. Of course, it also didn't make much sense why I or anyone else would utter this or any other name in many of these situations.
When I stub my toe on the coffee table, one might hear "Jesus Christ!" This is still true today, atheism aside. Why? It is so ingrained in me after several decades of hearing it used like this that it feels automatic. I never stop to think about it - or anything else - in these situations. Just yesterday, my favorite bowl - one in a matched set I haven't seen on sale for years - slipped out of my hand, hit the floor, and shattered. "Jesus fucking Christ!" I had a good laugh about that one afterward, but it makes little sense that something like that would pop out of my mouth these days. Granted, I'm no longer dissuaded by the whole "lord's name" nonsense, but still.
As a child, my parents and some other adults used Christianity (and sometimes Santa Claus) to control my behavior through fear and guilt. It was successful to some degree in shaping my behavior; however, it was a miserable failure in many respects. This issue of not taking "the lord's name in vain" was one of the areas where it crashed and burned. When I was a believing Christian, I tried to avoid saying things like this. I was not very good at doing so, and this led me to feel guilty and fearful too much of the time. Eventually, I stopped trying so hard. Once I realized I no longer believed in gods, I discovered that this fear and guilt had been taking a toll. I decided I was not going to worry about it any longer.
There are still plenty of situations in which I watch what I say, and I refrain from saying things like "goddamn" or "Jesus Christ" when I am in the company of people I do not know well or who I know to be particularly devout Christians. When I encounter someone who cannot seem to complete a sentence without profanity, I find that I tend to question the merit of their contributions more than I would otherwise. And so, I try not to use any of these words unnecessarily. But when I'm in pain, have just broken something I like, or find myself in some other situation that calls for it, I let them fly without worrying too much about any lords.