When you first start out and everything is very new it is very stressful.
When your new you don't know or understand the soft skills and you have to think what your doing and what your going to do next. Your also poo scared you will loose your license because of a brain fart mistake.
I have been flying now 21 years and 19 years commercially and 17 years as a Captain and done various training roles. So I know what people are looking for and know that the biggest crime is not communicating. The examiners don't care about brain fart mistakes as long as you communicate that you have done them and then sort them out.
You also build up muscle memory and a third sense what you should do... Which is just experience and there is only one way to get it and that's by screwing up and flying. The problem occurs with repeat mistakes of the same type. The system after that can become untuck and the Dash crash in the USA has highlighted and they still haven't managed to develop a system to allow company's to see long term training issues over a pilots career so some people seem to float and job change every couple of years just before the Training boss has lost patience in them and is ready to fire them.
They actually tailor the sim to your experience level so the first session after qualifying they are very gentle with the first officers and only give them a small amount of rope to hang themselves with. 2-3 years down the line they will ramp the pressure up and start the are they ready to be a captain process.
Two old hairy aviators in the sim together as partners they will throw the book at you and all of you will have a great time. And when we finish early we won't be flying under london Bridge for fun there will be usually some extreme edge of envelope stuff we want to have a shot at.
But I have never had a failed sim or had a two hour debrief after one. Those pilots that have, may find the whole thing a lot less fun than I do.