"In the flow"

I have just completed my 2nd reflective writing piece for PIDP 3250 and find myself looking at the material from an instructor and a student perspective. The piece that specifically caught my attention is on page 27 - "learning must be sufficiently difficult to pose a challenge but not so difficult as to destroy the willingness to try." (Barkley, 2010, p.27). This is referred to as "in the flow". Right now I do not feel in the flow with my PIDP course and I'm trying to figure out why? Is the task too difficult? Are the time constraints not working for me? Are the instructions clear? Am I not motivated? Do I need face to face interaction? These are all questions that I will have to spend more time pondering and hopefully this will help me out in the future as I take on more courses.
I find it all very interesting as I feel this as a student and am now relating it to the course I am teaching. Our my students "in the flow" and how do I tell?  Last week I did a pre/post quiz to see what the students knew before the material was presented and what they knew after the lecture. The comparisons showed great improvement of new knowledge. I feel this helped me realize that the material given was in the correct zone and the students were able to pick up on the key concepts. At the end of the week a quiz was given on the same concepts and a number of students answered questions incorrectly that they got correct 2 days before. Does this mean they are not in the "flow" now? or was it the way that they were tested? Are they more nervous when they take tests and this is why the results changed? I still have many questions!
I guess in general this is what the PIDP courses are supposed to do, make you think!!! Maybe I am "in the flow!"

Barkley, E.F., (2010). Student Engagement Techniques: A Handbook for College Faculty. San Francisco, CA:Jossey-Bass.