The book explains that how fast you progress depends on you and your horse. My mare, for example, still has tons of stuff to learn - but she has always been a very spooky, tense mare. So right now, almost all of our work is on trails getting her to relax. But as she improves, I'm starting to go back and look at things I can work with her on in an arena to improve her balance and understanding, which will also help her become a better trail horse.
I've got a lot of horse books, but Sean Patrick's is easily my favorite book on training a horse. There are steps that I, as a beginner, needed help to do. That is OK. I hired a trainer to get us past those points. There are other steps that help me 'ride out' my horse, so she doesn't become a horse who just knows forward, left, right, and whoa!