Moving on to what Tchern said:

For me a lot of my writing is instinctive rather than calculated. Although I do consciously think about things that should be logical like plot and world building. But when it comes to characters and dialog and pacing, etc, I am more instinctive (subconsciously directed).

I don't believe in muse or anything mystical in relation to writing, but I can totally see how others might. But I have read, seen (movies,tv), and heard thousands of stories. I have known thousands of people. Somewhere in my subconscious I have absorbed a lot of this, and some part of me understands how I want my stories to be told and how different types of people behave, but my conscious mind doesn't have a clue.

Real people can't be defined by a list of characteristics; they are more complicated than that. And when I try to define my characters this way, they fall flat.

I trust my instincts in character development. That is all I meant by characters taking a life of their own. It comes from me, sure, but a part of me that I don't fully understand and can't consciously access.

I never meant to imply that everyone should have their characters swear for the dialog to be realistic. But the OP said that his/her dialog didn't feel realistic without the swear words. If I was him/her, I would trust my instincts, and if the dialog didn't feel right without the swears, I would put them in because that is how I write.

But I know everyone does this writing thing differently, and other members did give great advice in how to avoid swearing. I apologize if it seemed that I was saying that my way was the only way.