Sentence Correction

Though using MGMAT SC for the SC, i am not showing a considerable improvement.
I still get so many wrongs. Am i not using the book properly.
I heard students get a very good score after learning concepts.
I like the book very much and i learnt quite a lot but exhibit a poor performance on tests.
Why is this happening? Can someone guide?

Are you able to support each of your choices with the correct rule? Or do you ever use your gut feeling while choosing?

kasia, i always follow the rule, when i am not able to get the mistake, then ofcourse gut feeling.
i usualy finish SC in less than a minute, does that mean i am overlooking mistakes?

If a batsman is taught theoretically how to make 4's and 6's, he may be bold out in the first ball. A batsman needs huge net practice rather than theory. The more net practice you do, the more probability that you will get a century.
In case of GMAT, practice more and more problems. Only reading the concepts will not help you.
Read official gudies---10, 11, 12, 13.
Thanks.