Inner prayer is the prayer of a child of God, a sinner who has been forgiven and who opens up to receive the love with which he is loved, and who wants to respond to it by loving even more. However, he knows that the love he responds with is the one that the Spirit pours into his heart; after all, everything is grace from God. Inner prayer is a humble and simple surrender to the loving will of the Father in an ever deeper union with his beloved Son.
(Catechism of the Catholic Church, no. 2712)