Seriously? In my opinion, this four-letter-word is worse than the worst curse word. It’s self depreciating, self destructive, and just plain wrong because there is no such thing. So just don’t say it.
If ever you find you need a different word with which to replace this other naughty one, try these instead: Won’t, shouldn’t, am not allowed, illegal, it’s wrong, I’m afraid, incapable, don’t want to.
Doesn’t matter what it is, it can be done, and by you. But first you have to believe in yourself.
That is all.