It's strange. When I was younger, I was usually able to watch my mouth (unless I was really angry for whatever reason). Sometimes a bad word slipped, but for the most part I kept clean.
When I joined the Army though, I began cussing quite frequently (not every other word, but I found myself using it in casual conversations. I think part of it was cause a lot of other soldiers cursed a lot too, and it kind of rubbed off on me).
Nowadays, I will generally only swear if I'm talking with friends, and even then, I try not to do it too much. I usually try to avoid typing swear words while posting online, although sometimes I let one or two slip out as well, depending on the mood I'm in and sometimes the content of the stuff I'm replying to/asking about online.
In a professional setting though, I can watch my tongue pretty well, and never use them when talking to my supervisors/superiors.
I hate to say it though, sometimes cussing is a little easier way to express my thoughts
Jam it back in, in the dark.