Don't criticise, condemn or complain

I just started reading Dale Carnegie's How to Win Friends and Influence People.

Principle no. 1 is: Don't criticise, condemn or complain.

But can I disagree? Not with the principle, I mean in general. Can I set myself apart?
What to do at the repetition if an error? Is there a point at which patience is justifiably lost?

Work scenario: colleague makes a mistake and denies responsibility. How do you know he won't repeat it? Ok I leave him the blame but take responsibility. Change the system. And I guess at some point changing the system means changing the colleague.

In personal life, same, I guess. In these relationships: don't criticise condemn or complain but do converse.

Ok, that's also called "thinking-while-typing".