Perseverance in Prayer.

"Our sinfulness, however grave, should never be an excuse to abandon prayer, contrary to what we may imagine or the devil may suggest. Just the opposite: the more wretched we are, the more motivated we should be to do mental prayer. Who will heal us of our infidelities and sins if not our merciful Lord? Where will we find health for our souls except in humble, persevering prayer? “It is not those who are healthy who need a doctor, but those who are sick. I have not come to call the just, but sinners” (Mt 9:13)." 

- Time for God pg. 36. 

Many times we are discouraged from prayer by our sinfulness and we think that God will not listen to us because he is disappointed in our sinfulness. This happens to me and probably to others too, and is a common "road block" to prayer. Our sinfulness only calls for even more prayer, because through our sinfulness, we fall and must be built back up with prayer. Prayer gives us the grace to get better and to overcome our sin. Prayer shows God that we are persevering and do not wish to sin again. We must ask God in prayer to help us with our sin and make us better. When we are in the state of sin, that's when we need God the most. God is merciful and he will forgive us but we must make amends to do better and obtain the grace to do better through prayer - we have to work at it! 

Saint Faustina summarizes this in an excellent way:

"Prayer -A soul arms itself by prayer for all kinds of combat. In whatever state the soul may be, it ought to pray. A soul which is pure and beautiful must pray, or else it will lose its beauty; a soul which is striving after this purity must pray, or else it will never attain it; a soul which is newly converted must pray, or else it will fall again; a sinful soul, plunged in sins, must pray so that it might rise again. There is no soul which is not bound to pray, for every single grace comes to the soul through prayer."