"Reflection is a one of the most crucial factors that keep a teacher going: We act, reflect, get feedback, read and act again. Feedback obviously may not always be possible, but without reflection, teaching tends to be dull, boring and ineffective on the part of not only the teacher, but also the students."

I am particularly not sure whether I used these two phrases correctly: "keep sb going" and "on the part of sb". Your feedback is truly appreciated :)