I'm over the defeat but unless he wins WTF then I think he's underachieved a lot this year and I'm sure he'll feel the same way.
There's no arguing that the top three players on the tour have been Federer, Djokovic and Murray with Murray arguably being the second best throughout the year so to not win a slam and only to make one slam final is a bitter pill to swallow.
He has underperformed at slams compared to his consistent level throughout the year, particularly at Wimbledon and US Open. His best chance was actually at AO where he was in excellent form, had a comfortable draw to the final, and Djokovic was not really at his best. He just wasn't ready to hang mentally with Djokovic for a full match at that point after all the beatings in 2014... obviously at the time, while disappointing, it was still great to see him reach a GS final and beat the likes of Berdych and Dimitrov in slams after the questions left by 2014. Looking back now it is more frustrating as that was the slam where things came together best for him.
Hopefully he can maintain the same (or even better) level in 2016, and then he has 4 chances to be at his best for one of the slams (and if he can keep up a similar level on clay he has a chance at RG too now - I actually feel he's more likely to do well there than US Open these days). And there is also the Olympics next year...