Quote from Virtuoso:
For the same reason most find it impossible to turn 25k into 100k; fear... I
My guess would be that you have become overly conscious of your initial feat, so much so, that your ego has become somewhat inflated and your mind has created the image of yourself as a "great" trader, or even just a competent one. Either way, any evidence to the contrary is going to cause pain, which overtime will manifest itself in fear. Fear that you cannot live up to the illusion your mind has created of "you the trader". Nothing scares a human so much as the possibility that the mask he has created for himself may one day get ripped off and he might one day have to face his "true self" in the mirror.