"Whatever you ask in my name, I will do, so that the Father may be glorified in the Son"
It seems to me that the person who is about to pray should withdraw for a little and prepare himself, and so become more attentive and active for the whole of his prayer. He should cast away all temptation and troubling thoughts and remind himself, so far as he is able, of the Majesty whom he approaches, and that it is impious to approach Him carelessly, sluggishly, and disdainfully; and he should put away all extraneous things.
This is how he should come to prayer: stretching out his soul, as it were, instead of his hands; straining his mind toward God instead of his eyes; raising his governing reason from the ground and standing it before the Lord of all instead of standing. All malice toward any one of those who seem to have wronged him he should put away as far as anyone would wish God to put away His malice toward him, if he had wronged and sinned against many of his neighbours or had done anything whatever he was conscious of being against right reason.
And although there are a great many different positions for the body, he should not doubt that the position with the hands outstretched and the eyes lifted up is to be preferred before all others, because it bears in prayer the image of characteristics befitting the soul and applies it to the body. I mean that this position must be preferred barring any chance circumstance. For under certain circumstances it is allowed to pray properly sometimes sitting... or even lying down... And kneeling is necessary when someone is going to speak against his own sins before God, since he is making supplication for their healing and their forgiveness. We must understand that it symbolizes someone who has fallen down and become obedient, since Paul says, "For this reason I bow my knees before the Father, from whom every family in heaven and on earth is named" (Eph. 3:14-15). And spiritual kneeling is called this because every single existing creature at the name of Jesus has fallen down before God and humbled himself to Him. The Apostle seems to me to indicate this by the phrase "That at the name of Jesus every knee should bow, in heaven and on earth and under the earth" (Phil. 2:10).