One day teacher of English A said to teacher of English B, “I’ve recommended you to plan each class: maybe one or two goals, some activities to implement during the class, combining listening with speaking, etc. However don’t plan too many things: with your experience you’re getting capable to plan the class and some useful activities in not much time – you know what your students need, what they enjoy, what you can demand from them, etc.
Now I tell you not to plan one class, next class, for example. Don’t be afraid. You, maybe somehow inadvertedly or unaware, know what fits in that class, and you have your real students in your mind – you do know them. Sometimes you’ll see that that class turned out well, even better than some very much outfitted and planned classes.