The man who does not humble himself and does not cleanse his heart from evil desires fasts in vain. He may eat nothing at all, but it will be to no avail if there is evil inside him. He must first cleanse himself from the evil within in order to receive the Lord.
If the soul is vigilant and withdraws from all distraction and abandons its own will, then the spirit of God invades it and it can conceive because it is free to do so.