The lessons of art history are that they are lessons. That is a tautology, but an illuminating one worth elaborating upon. It is necessary to know history as personal empowerment for artists: to test the present with the often surprising facts of the past, to note how and why "official" history has often changed; second, to discover one's own personal, vital ancestry; and finally, in order to criticize and change art history.
A short Artecdote about how our time, Postmodernism, resembles and indeed IS a form of Mannerism.
A short Artecdote concerning the difficulty in teaching an overview, or intro survey to Sub-Saharan African art, plus a free art image bank to download. Image bank link: http://brandl-art-articles.blogspot.ch/2016/10/african-art-course.html
A short artecdote discussing how criticism and complaint about the moribund artworld is important, but what positive things we can do to improve the situation.