For however much after our heart’s desire affairs may prosperously flow and occasion for happiness surround us on all sides, still there is no point of time when our need does not urge us to pray. A certain man has abundant wine and grain. Since he cannot enjoy a single morsel of bread apart from God’s continuing favor, his wine cellars and granaries will not hinder him from praying for his daily bread. Now if we should consider how many dangers at every moment threaten, fear itself will teach us that we at no single time may leave off praying.
Calvin, Institutes, III.XX.7