I really don't know what I can say to make you feel any better or not, but to be honest with you, I have gotten a lower score than you when I started. I did go through the phases of depression and thinking that I was in a way stupid since a lot of people in this forum get 680 and above. I have not taken the real GMAT yet, I am still preparing and I will find out in a few weeks how I do. But one thing that I have learned so far from this experience is that you should not let GMAT consume you so much emotionally. It only gets worse then, I have been there and done that. I was able to get out of my slump by realize how Blessed I was for having the opportunity to study and the opportunity to continuously learn. Yeah we all want to do well so that we can get into a great insitution, but it is also imporant to realise that if we don't get there, it is not the end of the world. I have not even broken 600 in any practise exam yet. But guess what, from where I have started and where I am now, I am very proud of my accomplishment no matter what others say or think. I believe that you may need some rejuvanation of the spirit. Refocus on your reason why you want to attend an MBA program and try to find that inspiration and motivation that is only inside of you...
Good Luck...