I think this is harsh on Nadal. Djokovic didn't beat himself, Nadal beat him. And it's not like Djokovic was struggling at this tournament, he breezed through every match in straight sets until he came up against Nadal.
Nadal can make anyone look bad on clay. If Djokovic is missing shots, this is often because Nadal is putting him in a position where he is likely to miss them. If Djokovic is making "unforced" errors, then likely this is because he is trying too hard, going for riskier shots because he knows that anything less would not be good enough against Nadal.