Sakura's cry had brought instantaneous silence across the false landscape. Everything froze - rain, flames, even the rumbling of the earth beneath her feet. In complete contrast to the nightmare Kakashi had presented for her, there was peace in a background of horrifying conditions. Bit by bit the imagery had faded from her eyes and senses, until she was returned to reality with the copy ninja in front of her, just as before. Releasing the seal in his hands, he had begun to inspect her for signs of mental fatigue. Breaking out of that genjutsu wasn't designed to be easy, but her effort had not gone unnoticed. Within a few days it was possible that she could overcome that level of technique. 

"Not bad, Sakura." Kakashi offered praise, even if she hadn't actually broken out of the illusionary technique herself, "I raised the pressure to show you just what high-level genjutsu you may come across someday. While we're working on your ability to perform the water dragon technique, I'll constantly send mental attacks towards you in order to increase your fortitude. Awareness doesn't hone itself." 

Before this training would conclude, Sakura would be dreaming of one word: Repetition. Hostile attacks to her mind while her body struggled to keep up - this was what it meant to push yourself to the absolute limit. 

For another hour Kakashi would send Sakura into the same scenarios just presented to her. Each time she cried out for him to end the technique, Kakashi always hesitated more and more. Whether she was able to recognize her progress or not, Kakashi was the one who was noticing it the most. Throwing her into thrashing oceans and planting her in the middle of raging infernos could only be considered extreme by the most easygoing of teachers. The truth was that she had to catch up to Naruto and Sasuke, not just because she wanted it, but because he [i]himself[/i] wanted it for her. Without a window of where he should stop, he chose to read her face and her body. Any longer and she might really pass out. 
[i]
She's definitely got heart[/i], her teacher couldn't have been prouder, inwardly encouraging her to keep going until she would finally concede.