Hello Aspirant,

Confidence develops through proper practice of questions, if you are solving mock tests on NTA Abhyas app then you should try to solve those questions by yourself without seeing it's solution in different books because this will make you realize that you can do it on your own. Suppose if you are unable to solve that question on that time so leave it for the time being but after  completing that mock test try to solve that remaining question by seeing it's solution or going through your notes and after solving that question search some more questions based on that concept and then try to solve them on your own, this will develop the clarity of concept in your mind.

For accuracy, solve as many previous year papers as you can along with different sample papers in the given time limit.

I hope this information cleared your doubts.

Good Luck!!