Fasting, neither above nor below your ability, will help you in your vigil. One should not ponder divine matters on a full stomach, say the ascetics. For the well-fed, even the most superficial secrets of the Trinity lie hidden. Christ Himself set the example with His long fast; when He drove out the devil, He had fasted for forty days. Are we better than He? "Behold, angels came and ministered unto him (Matthew 4:11)." They are waiting to minister to you, too.
Fasting tempers loquacity, says Saint John Climacus. it is an outlet for compassion and a guard upon obedience; it destroys evil thoughts and roots out the insensibility of the heart. Fasting is a gate to paradise; when the stomach is constricted, the heart is humbled. He who fasts prays with a sober mind, but the mind of the intemperate person is filled with impure fancies and thoughts.
Fasting is an expression of love and devotion, in which one sacrifices earthly satisfaction to attain the heavenly. Altogether too much of one's thoughts are taken up with care for sustenance and the enticements of the palate; one wishes to be free from them. Thus fasting is a step on the road of emancipation and an indispensable support in the struggle against selfish desires. Together with prayer, fasting is one of humanity's greatest gifts, carefully cherished by those who once have participated in it.