So, swearing in fiction. I'm guessing you either love it, or hate it. For me, too much, and it becomes tiresome.
I have used a few mild curse words (real and made up) in some of my fiction, but I prefer to steer away from it, if I can.
I've heard authors say that you have to use swearing, because it makes your fiction more realistic. Well, hold on a second there. When has dialogue in books ever been realistic? It isn't. Dialogue is stylised, or there would be ums and ahs all over the place - should we put all those back in, as well? And what about all that boring stuff that we have in our normal conversations that gets excised from book dialogue - do I have to double the length of my book to be realistic? No, I don't think so.
Plus, maybe I've led a sheltered life, but I've never experienced people swearing a lot in general conversation. And even if they do in some places, does it matter? I think it's similar to the representation of accents - a little can go a long way.
So, you're never going to find a lot of swearing, if any, in my books. I just don't think it's necessary.