I usually type quickly without looking at the keyboard using my own 10-finger-system I developed naturally (never bothered to train the official one). Though it allows me to type long texts quickly, I sometimes mistype words. Usually, though, it's not the same word over and over again. However, when it happens (sometimes I am just tired or I might have a strange mood~), I start typing that word more slowly, even watching my fingers on the keyboard, down to a tempo at which I can better control my fingers and stop mistyping. When working on a long text, I usually can increase the speed after a while again.
To put it in a nutshell, my advice would be to watch out for words you regularly mistype and slow down. Concentrate on the word, on the fingers. How do you type it, which finger hits which button and in which order? Get your fingers to memorize the word slowly, then increase the tempo naturally as you feel more and more confident typing the word correctly :)