This is a stinging rebuke by one of our early church fathers, and in my opinion the last line is the key --

"To profess to teach others what you yourselves are ignorant of, and publicly pretend to know what you do not know!"

If what we preach doesn't set our souls aflame, and the things we do are not what feeds our soul and devotion to Christ, we have little to say. No person has come to perfection, none are filled with all the graces, but we must preach from true experience.