During the time that the body of one fasting becomes thin and light, the spiritual life attains to perfection and reveals itself through miraculous manifestations. The spirit then performs its actions as if in a bodiless body. External feelings are as shut out, and the mind, renouncing the worldly, ascends to the heavenly and becomes completely immersed in the contemplation of the spiritual world. Yet not everyone can take upon himself strict rules of abstinence from everything, nor deprive himself completely of all that serves to relieve infirmities: "He that is able to receive it, let him receive it" (Mt. 19:12).
St. Seraphim of Sarov