Greetings tel93,
first order of business - heads up; don't beat yourself up if you scored below your expactations. take a different approach - learn from your mistakes, evauate your areas of weakness and develop a study plan to enforce the fundamentals in those areas of improvement.
second - don't rush things , taking the GMAT more than once is not the end of the world, its not worth it to apply when you're not ready. it is better to delay your entrance with a semester of a year but have a better score and better application, than submitting one that is rushed.
last, but not least - dude, take a break. a few days, a week or whatever you need to cool down; do something fun, enjoy life. hope that helps. take care and good luck.
kayser