Repentance means abandoning your previous way of life and acceptance of a new approach to God. This involves honesty , humility and renunciation and seeking God forgiveness.
The main reason we do not want to admit our sins.We may believe that admission of same may present us to others as we being weak or ineffective as a true champion as we may appear to others.
It is difficult to say how many are guilty but we all are at sometime or the other fail Him.