"If you know you are needy and believe that God helps the needy, you will pray. Conversely, if we seldom pray, the problem goes much deeper than a lack of organization and follow through. The heart that never talks to God is the heart that trusts in itself and not in the power of God. Prayerlessness is unbelief."
Kevin DeYoung, Praylessness is Unbelief (read the full thing here)