The first thing that they have you do in your credential program is write lesson plans, or at least that's how it seems as I look back on it now. As a teacher with some experience under my belt I now know, for a fact, that lesson plans are not the most important thing.
There are lots of things that I need as a teacher. I need to see my students as people, as individuals, as learners. I need to be able to adapt and learn as I go. I need to have a road map - a guide - to understanding the path I plan to take as a leader to help guide my students in their learning.
Now I realize that the only time I need a formal lesson plan is when I am required to write one for an official observation. Once in my credential program I was marked down on a formal observation because I deviated from my written lesson plan. It did not go the way I had planned or expected.
I realize now that they almost never do. Teaching and learning are organic - always evolving and changing. It's guess work at best, highly educated guess work, but guess work nonetheless. What would happen if a student asked an unexpected or unanticipated question and I refused to address it because it wasn't part of the plan? How am I supposed to lead a discussion if I am constantly trying to control its direction as opposed to my students?
Lesson plans can be a great help to a new teacher, if they are implemented in the right format and for the right purpose. Much like the Pirate's Code they are more guidelines than a set of rules. What I'm trying to say is don't limit yourself. Make plans, but let your class be your class. Don't let them limit you.