When you constantly listen to that inner voice that seems to hold you back or hold on to habits that keep you away from what you desire most in life, you are simply undermining your way to success. Self-sabotage is in itself some weird sort of defense mechanism for overthinking all of your self-improvement decisions.
It is your subconscious trying to take cover, protect you, prevent pain, and tackle fear. The sad thing about this defense mechanism is that you end up hesitant about taking chances. You become paralysed with inaction.