The unfortunate truth of being a pilot is you are regularly in the middle of a whirlwind storm of bs and expected to happily complete complex tests at the same time. No big deal. Half of being a pilot is letting stuff roll off your shoulders. The art of not being worried while at the same time genuinely caring about the task at hand is difficult and must be mastered over time.
There is nothing to be confused about. You have a goal (the cfi ride), to complete that goal you must do task A. Task A isn't attractive so it is making you nervous. You had a brain fart on your cfi ride, and paid the price, so that is adding to the anxiety. Completing any goal is the art of a thousand tiny corrections. Failing a CFI ride and then retaking it is a just another tiny correction. Society in general is engineered to tell you it's a humungous big deal, it's not. If you are still breathing, life is good. End of story. Everything else is an illusion set up by old grumpy dudes so they can justify their existence to the world.
This doesn't mean things aren't important, it just means that you need to realize that everything is a game that is trying to convince you it's not a game. It's a game.
Do what you have to do to complete your CFI. So what if you have to pay a DPE $800 and he is a complete pain to deal with and the entire day is unpleasant? A lifetime of wondering what could have been is worse. Accomplishing things means repeatedly doing things that make you extremely uncomfortable, which is why most people accomplish nothing. If you are comfortable, you aren't progressing. Never accept comfortable. Ever.
At the end of the day, no matter how things went, you still go home, drink that ice cold beer, and watch some TV.