I never really placed much faith in GPA as an indicator of my own or other people's abilities. Not simple because they can be easily inflated, but more so that everything you do in a class can be misleading. Classes are obviously structured, you get a directed level of difficulty at a certain level of intensity all subject to the professor's and/or the department's preferences. So, if you follow the path setup before you, bust your butt, most physics students can master what has been laid out and come away with a 4.0 because the material is limited. However, turn away from the preset path and dig deeper, pretty quickly you'll be coming across levels of physics and mathematics that can make you feel stupid. You'll even often times come across physics problems that should be easy considering your preparation that are somehow not. I found every class I've taken, every research project I've worked on to be incredibly humbling because of that result. I think physics is an ongoing gut-check, that naturally brings people down a peg at each turn. You can't try and understand the reality around you without coming to terms with your own, it's not a closed system. So, the point of that really is this. What motivated me was the observation of the professors I respected the most. They didn't sit there and lecture me on all the things they knew, on how they've forgotten more about physics than I know, all they ever did was show genuine excitement over all things they didn't know, just like myself. The reality of that situation however is that they had to bust their butt and knock out tests like the GRE to do this. I know I don't know a lot, in fact in the grand scope what I know couldn't fill a thimble. That's not okay with me, I'll never know everything or close to that but what I know now is not enough nor with it ever be. So, if I want to do something about it I have to deal with this horrible, boring, completely bull-crap exam to keep going in the manner I want to, to be able to do the research I want to and master the subjects to as far as they go or I can go. I may hate the politics of where I'm heading, hate the pay, not know if a job is going to be there when I get out but like the professors I admire I have to go through this grueling process just to get a shot. My motivation was that I wanted a shot to keep going more than I wanted to save some blind confidence in my abilities, more than I wanted to sleep, or go party with friends. If you can get into the mindset of just deciding that you're going to prepare like crazy, not with the goal only scoring well, but so that you can absolutely demolish this test then your chances are good. If you bomb, well, maybe you can retake it and hopefully improve, just try and identify where you were weakest. If a retake is out of the question, just say screw it, if you can't get past bombing even a big exam graduate school is going to be a journey into hell. In the end, your motivation has to be that you want to do this more than you want do anything else, and that the gre is a hurdle in the way that you need to get over. If you have doubts, if you can't honestly tell yourself that you want it that bad, you may want to consider reexamining if graduate school is the right path. I'm not saying even then that it isn't, but I'd take a second longer and harder look at what it is that I'm trying to do and why.