Just from personal experience, I canceled my score early Feb last year and retook the test in Oct. Im glad that I did knowing I did not do even close to how I did in Oct after taking a prep class. Im not sure if it will effect my applications, I have been accepted to four of ten schools so far, deferred at one and waiting on the others. Personally, I think it is better to cancel if you KNOW you did not do well because deciding to retake it later and averaging is painful. But if you feel you did well you might let it ride. Good luck either way!