It is such a heart break! I was doing really well with my practice exams scoring about 670 max to 580 min. And with the real thing :
1.I had timing issues in verbal section during my practice tests, ending up guessing the last few questions. In the real thing, I made sure i was awake and on and finished the section with 5 mins to spare. Felt questions were easy, did not challenge me.
2. Never had any trouble in quants during my practice tests, scoring on avg 46 and finishing on time. In the real thing, finished the quant section with almost 10 mins to spare. Felt the questions were easy, few were nice ones.
3. I have been prepping for the past 3 months.

Materials used :
OG 12
Kaplan Premier program
Princeton Review (i thought was a waste)
OG verbal, Kaplan Verbal Review
Kaplan Quant
Kaplan 800
Manhattan SC
Sahil SC notes

Few things, I took the MGMAT Tests each day, the week before the real thing to build my stamina. Thought MGMAT tests would have added better value to my prep, if i had them earlier.
Guys, I have an urge/temptation to take the test as early as first week of oct to prove a thing to myself (call it ego). Your inputs would be of great value to me.

I think taking a practice CAT each day might have burned you out.. a 21V means you probably couldn't concentrate on reading the verbal passages.

The last week, you should study light but not try to learn anything new. Just keep your brain working, but don't tire it out. daily CATs is overkill.