All the forms of demonic delusion to which the athlete of prayer is subject arise from the fact that repentance has not been set as the foundation of prayer, that repentance has not been made the source, the soul, the goal of prayer.

Saint Ignatius Brianchaninov
“On Spiritual Deception”

Beloved, how can we offer heart-felt prayer if our mind, heart, and will is not turned to our Lord? Cain’s sacrifice was rejected  by the Lord for he held back, i.e. he did not wholly offer the best of his fruits. His offering was tarnished. When we pray half-heartedly, our prayer too is blemished for we are holding back and not making a spotless and blameless offering. worrying monk

O longsuffering Lord, Who are forbearing and patience with the works of Thy hands, accept our prayers and entreaties, offered Thee from defiled lips, minds mired by raging thoughts, and hearts that have not fully turned to Thee.