Luxury is the wolf at the door and its fangs are the vanities and conceits germinated by success. When an artist learns this, he knows where the danger is.

This quote is saying that when people become successful and admire their own success, they become too proud and they can be taken advantage of by luxury. Luxury will try to tempt them with all its material and financial benefits, and if an artist understands this, they will know to be careful and not become too proud because of their success.