I've always had great respect for teachers. My mom has been a professional teacher for much of her life, as have several members of my extended family. And I've always enjoyed learning, so I've appreciated anybody willing to dish out knowledge and wisdom.
I've dabbled on the borders of teaching. Certainly the outreach that I do, such as this blog, or talking to people about astronomy, or helping with workshops all involve some elements of teaching. I also was a teaching assistant many times when I was earning my PhD, helping professors to teach classes (usually by grading homework and leading discussion sections). But I've never formally taught a class.
That is changing this summer, as I am teaching a class for graduate students. And while I knew that it would be a lot of work, it is even more work than I was prepared for. And it is quite a draining experience -- after talking for an hour or more, my voice is shot, I'm tired, and just mentally and physically drained.
So, I am gaining a new appreciation for those who make a career of teaching. And I am also gaining respect for college professors who teach three or four classes per semester. I suppose with a little experience things get easier, but certainly never easy!