I recently took the GMAT and did not perform very well (390). Am I wasting my time seeking a MBA degree?
GMAT is only a test and the fact that you scored 390 doesn't mean that it is the end of the world or something like this, it means only that you were not ready to go and that's all.
Now, come to your question : If you assumed that getting a "bad GMAT score" means that you are wasting your time seeking a MBa degree, i think it is completely flawed and this could be a good AWA test
I think if you want some help on how to improve your score, please don't hesitate to share your experience : for how long you've been on the track ? what is the materiel you used to work on ? what are you scores on mocks ? what is the section you feel more comfortable with ? what is the score you are aiming for ? .....
KUDOS is the good manner to help the entire community.