Do not go about your prayer only by external postures. Instead, continually direct your mind with great reverence to an awareness of spiritual prayer.
Sometimes when you stand for prayer you will pray well immediately. Other times, you won’t obtain your aim even after striving hard. This is so that you will seek still further. Then, once you obtain it, you will hold this virtue inviolately.
When an angel is present, all those that besiege us depart at once and the mind finds itself much relaxed and praying in a healthy way. But sometimes the normal battle takes place, and the mind fights and refuses to relax, because it is stirred up by various compulsions. And yet, when it searches further, it will find what it seeks, for to the “one who knocks vigorously, the door will be opened.”