Drugs (especially ones as powerful as MDMA) can leave permanent imprints upon your consciousness, but I think that for most people, there is always a path to recovery and a path towards self-actualization. You might not be able to achieve the same serotonin levels that you previously possessed, but the serotonin level, is really just a high and a sensation, and is independent of your ability to think abstractly and conceptualize goals. The problem most people have is the inability to separate their emotionality from their rationality, and when you binge on MDMA your short-circuited emotionality can infuse your everyday actions, making it impossible to rationalize and think clearly. If you were foolish enough to let MDMA fuck up your circuitry permanently, well that sucks, but get over it, don't make the same mistake, and think of other ways you can lead a fulfilling life. This doesn't have to be just emotional fulfillment, although I imagine that it is important for MDMA users (given the drugs nature), and other endeavors may not seem nearly as attractive in comparison, but once again, it is not close to the only way to lead a fulfilling life.
If Helen Keller can become a world-famous author/speaker you have no right to say that your previous binges on MDMA has prevented you from fulfilling your destiny ;D