Have you ever set out to achieve something, big or small, and you hear a voice in your head telling you how terribly you will fail? Or do you sometimes think you are not good enough and you just cannot do it? Many people have had an experience with this voice. It is self-doubt. This taunting voice beats you into a corner when you want to stand up to the high winds of challenges in life. All it does is criticise you and make you feel worthless.