Hi Adi93,
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 practice scores can become - and it's possible that this has happened here. By skipping sections, taking the CATs at home, taking them at times that are probably different when you'll take the Official GMAT, etc., you have not been properly training for the FULL GMAT 'experience.'
Test Day involves a variety of really specific steps and parameters (including steps before the Test even begins - such as leaving your home, traveling, etc.). Every factor matters, including the psychological ones. When you sit down on Test Day, you KNOW that you're going to be in the Computer Lab for about 3.5 hours - but if you're just taking individual sections (or taking a CAT without the Essay and IR sections), then you KNOW that you'll be done in 1-2 hours. The attitude and energy that you use during practice will NOT be a match for what you'll need on Test Day, so it's not a proper way to practice. Thankfully, these issues are all relatively easy to 'fix', but you have to put in the necessary effort to take your CATs in a more realistic way. You should plan to research the time slots that are typically available at the closest Testing Facility - and how long it would likely take to travel to that location.
For your next CAT, I strongly recommend that you take one of the Official GMAC CATs and take it in a realistic fashion (take the FULL CAT - with the Essay and IR sections, take it away from your home, at the same time of day as when you think you'll take the Official GMAT, etc.). Once you have that score, you should report back here and we can discuss those results.
GMAT assassins aren't born, they're made,
Rich