What do you mean? It's seems obvious to me that you could rest anywhere during the process. There are no time limits implied.

You're not the first one who has said something similar, which makes me feel that the flowchart gives a slightly misleading impression (but I don't know how to fix that). Because for me personally, the actual mental process involved in "following" it is very quick and effortless - I get an emotion, I focus on it, and most of the time I know almost instantly what the appropriate action is. It's the opposite of exhausting, because instead of having to struggle against every single flash of negative emotion I get, most of the time I just automatically go "okay, don't need to do anything here, it's okay to have this feeling" and that's it.

Admittedly, if you don't yet have the skill for doing that, it might take more effort and practice. I'm not sure of exactly what the required skill is, but I think that having practiced mindfulness meditation has a big role in it.