Hello Vinod,
The exam simulator is an excellent tool for learning, especially if you're reviewing both your incorrect and correct answers. This is time well spent.
If you are not doing as well as you hoped in a given process group, spending more time on those types of questions will be beneficial.
Getting enough sleep is crucial for your brain's top performance, as well as taking occasional breaks so you don't burn out.
Best of luck to you!
- Gail