I concur with the good priest's analysis that this is the heart of the matter:
The purpose of fasting is to gain mastery over oneself and to conquer the passions of the flesh. We don’t fast because it pleases God if His children don’t eat, "the devil never eats" (Lenten Triodion). We don’t fast in order to afflict ourselves with suffering and pain, that doesn’t make God happy. Neither do we fast with the idea that our hunger and thirst can somehow serve as a "reparation" for our sins. This understanding is never given in the Scriptures or the writings of the Saints which claim that there is no "reparation" for man's sin but the crucifixion of Christ. Salvation is a "free gift of God" which no "works" of man can accomplish or merit. We fast, therefore, and must fast, only to be delivered from carnal passions, to be delivered from our bondage to sin and to our own desires. We fast to make ourselves receptive to the operation of grace in our lives. So that we can become the dwelling place of the Holy Spirit.I commend to you the entire message.