I think that he is just disappointed. it became clear quite early on in the season that, whilst he had talked of a three year plan, he was really looking for promotion in year one. Although many of us knew that this was not realistic, I do not believe that many, if any, were predicting relegation.
Milan is upset. As with any successful person, he has grown accustomed to saying, "I want", and getting. To have invested, not just a heap of cash, but also his heart into this club and, in the first year, being so unsuccessful, hurts. He is not, however, a quitter and I will be amazed if he doesn't bounce back more committed than ever.