A word from John Chrysostom:
Do not be ashamed to enter again into the Church. Be ashamed when you sin. Do not be ashamed when you repent. Pay attention to what the devil did to you.
These are two things: sin and repentance. Sin is a wound; repentance is a medicine. Just as there are for the body wounds and medicines, so for the soul are sins and repentance. However, sin has the shame  and repentance possesses the courage.
I beg of you, pay careful attention to me, so you may not confuse the order and lose the benefit. There is a wound and there is a medicine, sin and repentance. Sin is the wound; repentance is the medicine. In the wound there is rottenness; the medicine cleanses the decay. The putrefaction, reproach, and mocking are caused by sin. However, courage, freedom, and the cleansing of sin accompany repentance.
Pay attention carefully. After the sin comes the shame; courage follows repentance. Did you pay attention to what I said?
Satan upsets the order; he gives the courage to sin and the shame to repentance…
There exist a wound and a medicine. The wound has the rottenness; the medicine can cleans the decay. Could the decay be derived from the medicine, the cure from the wound? Do these things not have their own order and those things theirs? Is it possible for this to pass over to that, or that to this? Never!
The Fathers of the Church: St. John Chrysostom On Repentance and Almsgiving, p. 115