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.
Spiritual activity embodies Christ in our soul. This involves continual remembrance of the Lord: you hide Him within, in your soul, your heart, your consciousness.
A person standing at an open window hears the sounds from outside; it is impossible not to do so. But he can give the voices his attention or not, as he himself wishes. The praying person is continually beset by a stream of inappropriate thoughts, feelings and mental impressions. To stop this tiresome stream is as impracticable as to stop the air from circulating in an open room. But one can notice them or not. This, say the saints, one learns only through practice.
You must set about rooting out the very desire to have things pleasant, to get on well, to be contented. You must learn to like sadness, poverty, pain, hardship. You must learn to follow privately the Lord's bidding: not to speak empty words, not to adorn yourself, always to obey authority, not to look at a woman with desire, not to be angry and much else. For all these biddings are given us not in order for us to act as if they did not exist, but for us to follow: otherwise the Lord of mercy would not have burdened us with them. If any man will come after me, let him deny himself, He said (Matthew 16:24), thereby leaving it to each person's own will ... and to each person's endeavor: let him deny himself.
The Holy Fathers recommend 'moderate' fasting; one ought not to allow the body to be weakened too much, for then the soul, too, is harmed. Nor ought one to undertake fasting too suddenly; everything demands practice, and each one should look to his own nature and occupation. To choose among different kinds of food is to be condemned; all food is God-given, but it is advisable to avoid such kinds as add to the body's weight and appetite; strong spices, meat, spirituous drinks and such foods as are solely for the palate's enjoyment. For the rest, one may eat what is cheap and most easily available, they say. But by 'moderate' they mean one meal a day, and that one light enough not to fill the stomach to satiety.