Secondly, prayer nourishes our hope and confidence; for the oftener we speak with another, the more confidently do we approach to him.
Thirdly, it inflames our charity, and makes our soul more capable of receiving greater gifts, as St. Augustine affirms.
Fourthly, it increases humility and chaste fear, for he who goes to prayer, acknowledges that he is a beggar before God, and therefore humbles himself before Him, and is most careful not to offend Him, of whose assistance he stands in need in everything.
Fifthly, prayer produces in our mind a contempt of all earthly goods; for all temporal objects must appear mean and contemptible in the eyes of him who continually meditates on things spiritual and eternal.
Sixthly, prayer gives us incredible delight, since by it we begin to taste how sweet is the Lord. And how great this sweetness is, we may understand from this circumstance alone, that some I have known pass not only nights, but even whole days and nights in prayer, without any trouble or inconvenience.
In fine, besides the utility and the pleasure, prayer also adds dignity and honour to us. For even the angels themselves honour that soul which they see is so often and so familiarly admitted, to speak with the divine Majesty.
--St. Robert Bellarmine, The Art of Dying Well
(Formatted for easier reading)