It comes out of me whenever I am stressed like "F__k, I've got so much sh_t to do today" or "Where the F__k are my keys?" Sometimes I swear because I'm overjoyed about something. Like for example I'll say to myself "Yes, that's so f__k'in awesome!!!" Then I'll text my thoughts to someone as "That's really great, good for you." : )
I swear a decent amount around certain friends. In general, I don't swear much, but there are some friends who bring it out in me. It just depends on the context.
I save my special words for things like hitting my thumb with a hammer or being stung by a wasp. I don't use them in everyday conversation, they would lose their effectiveness that way.