Writing a journal is one of the most popular and widespread self-assessment and growth habits around the world. It is simple, since you do not need much to get started. After each lesson, take some time to write down a few things on how you are feeling and try to describe your observations. Based on what you have observed, decide how you will teach next time in order to improve both your own & your students’ experience.
If it helps, break down your journal into specific sections such as lesson objectives, classroom management, students, teacher, etc. This way you can be more consistent with how you measure your performance. We also advise you to ask specific questions related to these topics to get an even more detailed idea about your teaching methods and the lesson in general.