Some say that when a person prays he should have his mind on the icon or the words. No. Not on icon nor letters. Let him have his mind in his sinfulness, but with discernment. Many times the devil can cause trouble there too. He'll tell you that you are sinful, to make you despair. You should answer him abruptly: saying "What's that to you? When I want to say that I am a sinner I will and not when the devil wishes; because when the devil wishes he'll bring me to despair.