It must be neither cold, crafty, untruthful, nor double-minded, otherwise what will be the use of our prayers, of our preparation for the Sacrament?
It is good for us to hear God’s voice of anger: “This people draws nigh unto me with their mouth, and honours me with their lips, but their heart is far from me” (Matthew 15:8).
So do not let us stand in church in a state of spiritual prostration, but let the spirit of each one of us on such occasions burn in its working towards God.
Even men do not much value the services which we render to them coldly, out of habit. And God requires our hearts: “My son, give Me your heart” (Proverbs 23:26).
Because the heart is the principal part of the man – his life. More than this, the heart is the man himself.
Thus he who does not pray or does not serve God with his heart, does not pray at all, because in that case his body only prays, and the body without the mind is nothing more than earth.
Remember, that when standing in prayer, you stand before God Himself, who has the wisdom of all. Therefore, your prayer ought to be, so to say, all spirit, all understanding.
John of Kronstadt (1829-1908; Russian Orthodox): My Life in Christ