Confession — opening to grace

Let those who perform works of penance learn from the words of the prophet with what dispositions they must do so, with what zeal, with what spirit, with what purpose, with what inward compunction they must do so, with what zeal, with what spirit with what purpose, with what inward compunction, with what change of heart: "Look, Yahweh, I am in distress! My inmost being is in ferment; my heart turns over inside me.

So too did the people of Nineveh mourn, and they were spared the destruction of their city (see Jonah 3); so great is the remedial efficacy of penance, that God seems to change his decree because of it. It is, therefore, withing your power also to escape his punishment. He wants only that you place your hope in him, he wants only that you appeal to his mercy. If you ... are unwilling to grant pardon to your neighbor unless hea sks for it, do you think that, without your asking for forgiveness, God will forgive you?

Let us then mourn for a time, that we may rejoice for eternity. Let us fear the Lord; let us prepare to meet him, confessing our sins; let us correct our failings and make amends for our transgressions, lest of us too it should be said: "The faithful have vanished from the land: there is no one honest left" (Mi 7:2)

Why do you fear to confess your sins to the Lord who is so good? "Confess your sins," He bids you, "so that you may be justified." The grace of justification is offered you, while you are still guilty of sin; for he is justified who voluntarily confesses that he has sinned. ... The Lord knows all things, but he waits for your confession, not in order to punish but in order to forgive.

St. Ambrose,
via The New Jerusalem Bible (Saints Devotional Edition)

Saint Ambrose here is considering the words of Micah 7:18, "What god can compare with you for pardoning guilt and for overlooking crime? He does not harbor anger for ever, since he delights in showing faithful love." 

Micah, of course, is speaking to the Lord God, praising his lover and forgiveness. When we mourn our shortfalls, these are heartening, inspiring words, especially if we've fallen away from a close relationship with God. This is the time to bare one's soul and come back into a loving relationship who is like the father from the parable of the prodigal son — just waiting with open arms for us to come home.