The best teachers mix high standards and corrective feedback with appropriate praise and a genuine personal connection with their students.
Yes. This.
And sometimes-- in fact, I'd argue more often than not-- we lack the maturity or self-awareness
at the time to fully appreciate such teachers. They don't necessarily cultivate warm and fuzzy feelings from students, and most of them could care less about popularity.
We do work harder for them, learn more, and grow in ways that would have been impossible without their influence, but they may not provide us with a lot of "feel-good" moments IN the moment, if you see what I mean. In fact, my experiences in higher ed indicate that most such educators are viewed with a certain amount of dread and resentment because of the TIME they demand of students.
I can count a handful of such teachers in my life. I'm grateful beyond words to each and every one of them, including the one in college that reached the end of a rather long fuse with my slacker attitude... and tore into me rather assertively. With another student, it would have been "abusive." I blush a little even now, recalling that moment and feeling ashamed. For me, it was...
a teachable moment. I didn't ENJOY it, but I needed to hear that message, and I needed it to be unvarnished. This professor knew that about me and delivered.
Total home-run. 
