Hi born222,
Test Day is a rather specific 'event' - the details are specific and they matter, so you have to train as best as you can for all of them. The more realistic you can make your CATs, the more likely the score results are to be accurate. The more you deviate, the more "inflated" your scores can become. Skipping sections on a CAT or taking individual 'sectional' tests will not provide you with a realistic score result because neither of those types of tests makes you work through everything you'll experience when you take the FULL GMAT. As such, you have to be more detail-oriented about how you take your CATs (including taking the FULL CAT - with the Essay and IR sections, taking it away from your home, at the same time of day as when you'll take the Official GMAT, etc.).
1) How long have you studied?
2) What materials have you used?
3) How have you scored on each of your CATs (including the Quant and Verbal Scaled Scores)?
4) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich