I have been really struggling with this concept of a "learning journal" that we are tasked with in our assignments. In doing some reading on different websites, I came across the books written by Geoff Petty"Teaching Today" and "Evidence Based Learning".
Mr. Petty has a phrase "theory-in-use" that he uses to describe "What you believe learning to be, and how you believe teachers can bring learning about." (Petty, 2009). His advice is that we utilize this "theory-in-use" to guide us in how we choose, implement, evaluate and adjust our instructional strategies in our classrooms, effectively creating a "learning cycle".  A major part of this "learning cycle", is the use of the learning journal to record the strategies that we have laid out in our lesson plans, the response of the student to those strategies, listing what worked and how, as well as what did not and why. We then review and reflect on our results and set about keeping what worked and removing what didn't.

The key is to determine why a particular strategy worked. In one example given in Teaching Today (Petty, 2009), the teacher has used a classification game in her lesson plan for figures of speech where the students would decide which category each phrase fit, metaphor or simile. In her reflections contained in her journal she was able to determine what was successful in the lesson and why. The game was fun, so the students were willingly engaged. It displayed the students level of understanding and skill at applying it in a far less threatening way than had she simply given them a written test and then scored their work. Now the teacher is able to determine whether this instructional strategy of the "classification game", can be used in other areas of her "theory-in-use" for other lessons in the future.

Ref.
Petty, G.(2009) Teaching Today A Practical Guide. Cheltenham: Nelson Thornes
Geoff Petty - Improve your Teaching