When you are dealing with your difficult person, you can expect that they will get worse before they get better. This is a good sign.
We are all familiar with the old saying “If you keep on doing what you always done, you’ll keep on getting what you’ve always got.” We know that with our difficult person, we have to do something different. We know that we want to “push” them out of their normal/regular response to do something different (and hopefully less difficult).
You can expect that as you practice different responses, or different strategies, that you will confuse your difficult person. That confusion (or lack of a payoff on their part) will require them to do something different.
Expect that what they do will be to increase their “difficultness” (I realize that isn’t a real word). This means that what you are doing is actually working, don’t give in, keep on-the-right-track.