Pope Shenouda III
Fasting leads to virtues, which relate to the purpose of fasting.
The Apostles for example, prepares one for service. Nineveh’s fast, aims at repentance. The purpose of a fast, such as Esther's, was to save her people. There are those who fast for others and their fast embodies love, sacrifice, and cooperation. These are all fasts, which relates to with special virtues.
We should remember in our fast that the Lord Jesus Christ fasted while He was filled with the Spirit. As for us let at least fast so that we may become filled with the Spirit.