Changing lesson plans..... Quickly

I thought I should share about my day Friday. It stressed me out during the process, but I felt like a stronger teacher in the end. I planned a very interesting and real-world lesson where students were supposed to use their graphing calculators to find the distance away that a storm is by using the function y=0.2x. I gave the students step-by-step directions of what to push on their calculators to 'discover' their answers.
Sadly, my first class just wanted the answer and didn't follow directions given (you could not miss a step or it wouldn't work correctly). This caused a lot of the students to stress and me getting annoyed since hardly any student follows written directions anymore.
I altered my lesson for my next class where I verbally walked them through the steps. This worked, but we didn't have enough time to really analyze the graphs. So, I decided to go with plan B. I decided to break out the old overhead and SHOW them the exact steps and screens they should be on. Sadly, overheads are past their days and it decided to stop working for me 2steps into the process.
By this time, I was ready to give up. I have never had to alter my lesson 5 times in one day. I guess this was my test of being a strong teacher willing to make last minute changes. Thankfully I had prep my next hour and was willing to really change how I went about this lesson. I had to do something because I was being observed my next hour!
In the end, everything turned out alright. I spoke with the observer letting him know of my day and how my plans didn't work. He thought the lesson I gave went well and I actually felt good after the lesson was over. My flexibility throughout the day helped me grow tremendously. I will not forget this day for a long time.