No amount of practice or simulation will prepare you thoroughly for the stress you face during CAT. This is something which can only be experienced, not explained.
There are several factors that add to the pressure: Time, the standard of the questions, the unfamiliar setting, the quantity and quality of competition, etc.
CAT tests your ability to work under pressure for 120 minutes. A particular section may be unusually tough, but that should not affect the rest of your performance.
For various reasons -- nervousness, your choice of questions, etc -- you may find yourself unable to answer too many questions in the first half hour. Don't let this undermine the rest of your performance.
The uniqueness of CAT lies in its unpredictability.
The number of questions, their standard and pattern, the packaging of the test are all unknown and vary from year to year.
There is no preset formula.
Which mean, you have to be flexible.
This is not to say you should go into the examination hall without a plan or strategy. But the plan should be so designed that it can be adapted to unknown situations that may arise in the test.
It is important that you realise this so that your expectations are pegged within realisable limits.
The challenge lies in being aware of your strengths and weaknesses and working in such a manner that your plan factors in your weaknesses while exploiting your strengths to the fullest to maximise your score.
The difference between people who crack CAT and those who don't is not academic brilliance, but the qualities mentioned above.
While it is important that you are thorough with the basic concepts, you should also take these factors into account if your are looking for a good result.