Sorry to hear that things aren't going too well with the prep so far. Are you really really far away from a 700 at this point, or are you within reasonable shouting distance? Honestly, if your scores are low enough at this point, then it might not be realistic to cram like crazy for three weeks, anyway. The GMAT is oddly resistant to cramming, since it's mostly a test of logic and reading precision and time management; there just isn't all that much formulaic information that you can wedge into your head in three weeks. Sometimes you just need tons of practice over a long period of time to make a huge score improvement. So if you're hating the GMAT and you're a long ways from your target, then maybe it's best to just enjoy life before you start working?
If you're just finishing school, then it's definitely true that your brain is already in "academic mode," and you're probably better at studying than you will be in a few years. On the other hand, I think that it's awfully hard to stay motivated when business school is still several years away. Once you're partway into your career, you might end up being unbelievably passionate about getting an MBA, and that will fuel your studies. Sure, you'll have to shake off some academic rust in a few years, but if your desire to get a certain score is strong enough, you won't have any trouble getting fired up about studying.
I'm just guessing here, but it doesn't sound like you're all that fired up about studying for the GMAT right now. Again, if you're not that far from your target score, great--it'll feel really, really good to get the test over with. But the GMAT will still be around in a few years. If you're not feeling motivated and you're not doing well so far with your studies, there's not much harm in waiting. Hey, when's the next time you'll have three weeks completely off from both work and school? You might as well enjoy it.
I hope this helps!
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