I think Li Na tries to go for winners too much and doesn't work the point more. Li Na blew another grand slam final I don't think Azarenka played much better to be honest she was just more steady in the critical moment. Li Na lost this match due to making too many unforced errors.
Two times I thought Li lost the match was when she lead 3-1 in the first set had a chance to go up 4-1 yet blew an easy floater with a swing volley. Azarenka wins the game and gets back into the first set.
The second time was even worse, Li has a chance to make it 3-3 in the second set she has 0-40 on Azarenka's serve an open court and dumps the ball in the net on her third break point. Azarenka takes a 4-2 lead and wins the second set and eventually the match is over.
Li blew this big time just like she did against Clijsters in 2011 she seems to have problems winning when there is pressure for her to win.