Not to mention what's still hanging over his head, something he fears even more than his 'death' last season - the fields of Trenzalore, the "Fall of the Eleventh," the Question that MUST (never) be answered. (And he never did find out who blew up the TARDIS, did he?) He was already in a bad mood going into the events in New York; now after all this, and with his erasure from the very memory of the universe, it makes sense that the 1,300+ year old (at least) Doctor would decide "I've had it. I'm getting too old for this ****."
Interestingly this might call for a new pair of eyes(12th doctor)
Who might believe there's still stuff to be done out there
Not saying Matt smith is close to leaving