The 21-year-old returned to action in a 2-0 victory over Wigan in a pre-season friendly on Saturday, playing the first 45 minutes.
"When I had my first game on Saturday, I felt so emotional. It was the best feeling ever," said Shaw, who signed from Southampton in June 2014 for £30million.
"There was a fear of how long it was going to take or whether I would play again. Now I am looking forward to pre-season and getting fully fit."
Luke Shaw returned to action in the friendly against Wigan
"When I found Luke at the training ground, it was a surprise for me because I thought he couldn't be ready to train without any type of limitation," Mourinho told MUTV.
"But he did fantastic in the summer. He sacrificed his holiday. He stayed in Manchester and was at the training ground every day, putting himself in condition."
The Portuguese added: "Of course, you lose a bit of sharpness of condition and confidence, that is normal, but he is trying hard."
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