What a difference there is between a deeply exercised and spiritually burdened heart pouring out itself before God in fervent supplication and the utterance of verbal petitions by rote!  It is the difference between reality and formality.  He who is diligent in heart work and perceives the state of his own soul is at no loss in knowing what to ask God for.  So he who makes it a practice of walking with God, communing with God, meditating upon God, spontaneously worships Him in spirit and in truth:  like David, he will say, “My heart is inditing a good matter” (Psalm 45:1).  The Hebrew there is very suggestive: literally it is “my heart is boiling up a good matter”; it is a figurative expression, taken from a living spring, which is bubbling up fresh water.  The formalist has to rack his mind and, as it were, laboriously pump up something to say unto God; but he who makes conscience of heart work finds his soul like a bottle of new wine—ready to burst, giving vent to sorrow or joy as his case may be.  Arthur W. Pink, Practical Christianity