Patience
Stop fooling yourself in thinking that you just need to do or say just one little thing and then BAM! everything will be better.
It won’t.
It takes a strategy and a planned course of action to deal with your difficult person. It isn’t just one thing, it is a series of things that you do, and things that you say. What works today, may not work tomorrow – what will you do then?
Don’t give up – have many steps on your strategy and don’t get frustrated when it doesn’t immediately fix your problem.