In this way modern training has some similarities with koryu. There is a reason that the senior teacher is always in the uke role in combative arts. The senior should know just how much pressure the student can handle to draw the best out of him, while not crushing him, leaving him mentally depressed and defeated, and then sending him out to the wolves without the proper mindset.
As an instructor I am very aware of this when I train my guys. It is important to bring them along and walk the edge to bring out the best in them. Some times it requires totally dominating them to let them know that they have alot to learn. Most of the time it is working them in various positions, leaving opennings for them to see if they are picking up on them. Slowing down trying to get them to focus and relax, letting them reset, giving up position allowing them to dominate to see what they do, then exploding back out again and rolling to another positiion so you can work something else.
Some times you lose, the better they get, the more you have to start working. I love it when I finally have to start actually working hard to keep them from submitting me, then I know we are on the right track!