Persist in prayer when you know you are not worthy of being heard.
Three books to Bonosus, Bk.3,4; PL 112, 1306
“He will give him whatever he needs”You should never lack confidence in God nor despair of his pity… Sing to the Lord these words of the prophet: «As the eyes of servants are on the hands of their masters, as the eyes of a maid are on the hands of her mistress, so are our eyes on the Lord our God till he have pity on us.
Have pity on us, O Lord, have pity on us, for we are more than sated with contempt» (Ps 123,2-3)…
If we are sated with contempt because of our numberless sins yet our eyes should remain turned to the Lord our God until he has pity on us, nor should we cease to beseech him until he grants us forgiveness for our faults.
Indeed, it belongs to the steadfast and persistent soul never to desist from persevering in prayer through despair of being answered but to persist unwearyingly in that prayer until God shows it mercy.
So that you do not begin to think you are offending the Lord by persisting in your prayers when you are not worthy of being heard, remember the parable in the Gospel.
There you will find that those who pray to God with importunate perseverance are not displeasing to him, for it is said: «If he does not give it to him because of their friendship, he will get up to give him whatever he needs because of his persistence.»
Understand, then, that it is the devil who tempts us to despair of being answered so that hope in God’s goodness, anchor of our salvation, foundation of our life, guide for the path heavenwards, may be taken away from us.
Paul, the apostle, says: «In hope we were saved» (Rm 8,24).
thanks to : http://www.dailygospel.org