Think of something you are good at, and I bet you learned it by self-assessment.
That is, asking:

• What am I trying to do exactly?
• What went well and why?
• What went less well and why?
• How could I do better next time?

Carl Rogers places self assessment at the start and heart of the learning process. And the learning from experience cycle devised by Kolb places heavy emphasis on self assessment.

So get (back) into the habit of evaluating or self assessing (same thing) your lessons:

• Self assess a lesson or a typical lesson of yours against standards for excellent teaching. The download below describes standards for excellence, and asks you to comment on the extent to which you meet each standard, and how you think you could improve each one. (I wrote these standards for ‘Mentoring Towards Excellence’ a national publication written for the the then inspection and standards bodies, and the Association of Colleges. I have improved them since then, making them more evidence based.)
  Download standards for excellence.
• For a given lesson, ensure you have an effective strategy to discover what and whether your students have learned. Use this to self-assess the lesson. Try to do this often.
• Devise a questionaire asking students whether they learned and which parts of a lesson they learned most from, what they found most difficult etc. (Scary but informative!)
• Examine your teaching style by completing this questionnaire and getting your students to complete the other. Download teacher’s questionnaire. Download student’s questionnaire

It is most important that you reflect in a way that enables you to learn. This involves not blaming
your students or yourself for anything that went wrong. but instead trying to identify why things worked or didn’t work. Try to learn the general principles of what works, and then you can use these principles to work out how to teach better in the future.

If you are interested in learning from experience, or would like some help in writing a learning journal, you might find this short extract from ‘Teaching Today’ helpful: Download – reflection and journals

There is much more on the theory of self assessment and learning from experience
in ‘Teaching Today: a practical guide’ Geoff Petty, 5th Ed (2014) published by Oxford University Press.