A pious man does not pray by rote. He does not enunciate words thoughtlessly and inattentively like a parrot. Rather, he says every word with the thought and intention befitting it. His heart and tongue are at one with each other, for he will not express with his tongue what his mind does not truly think.
The time of prayer is the most important time of the day. The other hours are used leading up to it. In effect, the fruition of his day and night is the three periods of prayer.
Prayer is as vital for the soul as material food is for the body, for the soul's sustenance is prayer. The positive effect of one prayer accompanies him until the next prayer, just as one meal fortifies the body until the next. As time passes since the last time he prayed, his soul begins to feel darkness and melancholy because of its encounters with the materialistic world. During prayer, the soul becomes purified from these contacts and prepares itself for the stretch of time until the next prayer. (The Kuzari 3:5)