As a recommended best practice, it is a good idea to at least collect your thoughts on what you wish to express in your video and then create at the very least, a guide or outline with bullet points for reference to help you keep on topic.
I find that this helps me with certain videos in keeping me on subject and in making certain I cover everything I intended to.
However, I think you did an excellent job of winging it in this video. That leads me to conclude that you did put a lot of thought into what you wanted to express, even if you did not think it through to writing a script. Great job!