I believe Strayed’s transitions are effective, as spacers for the story and for illustrating the progression, the evolution of herself. Particularly the use of scenes, literally a the scenery around her changes. As she moves forward, so does the trail. This could be dismissed as redundant; thats the point of the book. But that does not take away from it’s accuracy. One example could even be her change from home to hiking on the trail. It is clear that decision was part of the initial change, and her character on the trail is grown from that at hme, seen through the flashbacks.
Another good use of the clear cut “parts” is the ability to link events and thoughts with the surroundings. The mountains, the rain, for example can be subgroups to link memories too. this provides for easier reliving and an organized plan, and in that way it may be written in this fashion to assist Strayed in accurately remembering everything, rather than her just writing freely until she seems to reach an end. That is chaotic and risky misremembering things. In this way, planning for the story would have been easy and helpful for her.