I never swear in public; as in 'anyone else in the room but me'. But I swear from time to time while alone, when I get mad or frustrated. Hypocritical, I know.
I did the same while I was 'in'.
What puzzles me - - and I have thought of making a topic of it of it's own - - is that I keep swearing using various euphemisms for satan and hell. Things I don't believe in - hell(!); - I never even believed in hell in the first place! In my language, it's more common to use swear words derived from 'satan', 'devil', 'hell' etc. than the physical act of lovemaking and various body parts, as is common in the UK and US.
It's as if I need those 'really bad' swear words, even though I don't believe in the concepts. It's just that they're considered 'bad', I guess, and one needs something with 'bite' to it if a swear is going to be 'effective'. I've tried making up new swear words, like 'mother of a teddybear-hugging sheep!' or things of that nature, but it's just not the same...