What is best and continuous self motivation for cracking the CAT during the preparation...

Preparation, Patience and Persistence is all you need which shall be repeated again and again untill you achieve satisfactory scores in your mock tests. All you need to do is focus on weaknesses, rectify them and dont repeat them again to optimize your efforts. Once, you do that gradually yo will surely gain a good score. In exams, you needto attempt questions which you are confident of in fastest time to get good score, so despite of getting average marks you can shine out well if you perform well with above mentioned strategy. Just believe in yourself and you will be unstoppable.

IIMs are not only for those people who have the excellent past performance or high IQ.

It does not matter how you have been performing in mocks or classes you can improve your performance with continuous effort and practice. If you think your past academic scores/work experience will prevent you from getting an admission even with a good percentile, that's not true, there are some excellent B Schools to welcome you and a life changing experience by getting into a premium institute. The exposure, learning and opportunities will be limitless and people have struggled a lot and succeeded whichever sphere of life it is. Begin now and conquer it.

If 100's of students each year can do it, so can you. It's not tough but just requires a structured approach.