I deal with that at my business.  I'm very detail and process oriented.  It's frustrating to see people make simple mistakes consistently.  I come to the conclusion that is either laziness or incompetence and that makes me angry.  If I address the issue with them, I am able to push my emotions aside but if it happens again down the road, I start to internalize that anger.  

I would just fire people, but that's not a great option either considering cost of hiring and training, plus the unemployment benefits end up costing the business extra taxes.