Really? How is this year more disappointing than, say, 2009 where he got kicked out of RG by Kohli and was outclassed on grass by Haasi? Didn't come close to a slam, and never made a slam final.
He was simply playing bad that year, and was nowhere near making some great result.
All his losses this year were caused by nothing else but his mental state, except maybe for Isner match. Take RG final for example. You can't take 8 straight games off Nadal on clay and then claim that you weren't good enough. Also US open final, comes back fro 0-2 and then goes awol in the 5th.
All in the head.
When I said disappointing, I meant it's so sad to watch him loose matches that he would have won easily with just half of last year's mental fortitude. You are supposed to become even tougher when you overcome such obstacles that he overcame, not the other way around.
This will all become evident next time he steamrolls Fed or Murray, as soon as one of them fails to stick with him from the get-go.
He will then proceed to loose another few tight matches and after that, he will either get his act together or start loosing comfortably to any in-form player that comes his way