The key is to develop a few solid criteria that you are going to isolate and track from student to student and day to day. These are a little like when a doctor asks “how does it hurt on a scale of 1 to 10.” It’s not that 8 has some unchanging in-the-eyes-of-God meaning. The point is that you can begin to get some quantifiable grasp of your changing perceptions by gathering multiple entries over time.
As teachers, we need to embrace our slime mold heritage. We need to seek more and more opportunities to feed our discoveries back into the network, and seek more and more opportunities to draw upon that network.
Teaching, if you are doing it right, is ALWAYS hard because learning, if you are doing it right, is ALWAYS hard. If it's not hard, then you are wasting time.