Hi Aman.
The following is interesting.
amangupta207
While giving the actual test, I found out the questions were relatively tough as compared to mock test.
Here's why it's interesting. The verbal verbal questions on the actual GMAT are of about the same difficulty as those on the official practice tests.
So, the question becomes that of why you found the questions on the actual GMAT harder than those on the practice tests, and the most likely answer is that something about the way in which you have been preparing for GMAT verbal has resulted in your being prepared for the official practice tests but not for the actual GMAT.
There are two common reasons why people have experiences like yours.
One is that whatever resources they used to prepare were based on the verbal questions on the official practice tests. In other words, those resources basically prepare people specifically for the questions on the practice tests. So, of course, in such a case, you'd find the questions on the official practice tests relatively easy, whereas the questions on the actual GMAT would seem harder to you.
The other is that you may have prepared in a way that involved learning what the GMAT has done in the past rather than developing fundamental reasoning skills that you could use to answer GMAT verbal questions from the past or from the present or future.
So, the key to increasing your score is to develop such fundamental skills that you can apply to correctly answer any GMAT verbal question you see.
For in-depth discussion of how to do so, see the following posts.
How to Score High on GMAT VerbalThree Key Practice Tips for Mastering GMAT Verbal