Answers to this question suggest that the 16 are steps or stages of anapanasati, which implies that they are a progressive sequence of steps or stages. They are also related to the four foundations of mindfulness or the satipatthana.
On the other hand, the booklet "How To Meditate" (quoted below) by Yuttadhammo Bhikkhu, seems to suggest that one should not use it as progressive steps. Instead, it recommends that if feelings arise, stop what you were trying to do, and go with that. Or if thoughts arise, stop what you were trying to do, and go with that.
That does not sound like a progressive sequence of steps. That seems to be more "go with the flow" or feel free to move from any of the 16 to any other, depending on what arises.
So, which is right approach to anapanasati? Are the 16 progressive sequence of steps approach right? Or is the approach of the "How To Meditate" booklet right?
Or are they two different techniques?
From "Chapter Two: Sitting Meditation" of the booklet "How To Meditate":
Regarding the body, watching the rising and the falling is sufficient for a beginner meditator. At times, one might wish to also acknowledge the position of the body as “sitting, sitting”, or “lying, lying” if it is more found to be more conducive for clear observation.
In regards to feelings, when a sensation arises in the body, one should fix one’s attention on it, discarding the abdomen and focusing on the sensation. If a feeling of pain should arise, for example, one should take the pain itself as a meditation object.
Any one of the four foundations may serve as a meditation object, as all four are aspects of reality. It isn’t necessary to stay with the rising and falling of the abdomen at all times. Instead, when pain arises, one should observe the new object, the pain, in order to clearly understand it for what it is, rather than judging or identifying with it. As explained earlier, the meditator should simply focus on the pain and create the clear thought, “pain, pain, pain, pain…” until it goes away. Instead of getting upset about the pain, one will see it for what it is and let it go.
When happiness arises, one should create the clear thought, “happy.” When one feels peaceful or calm, one should create the clear thought, “peaceful,” or “calm” until that feeling goes away. Here, the object is to avoid clinging to the feeling, which would create a dependency on it. When one clings to positive feelings, one will be inevitably dissatisfied when they are gone.
Once the sensation disappears, one should return to the rising and falling of the abdomen and continue observing it as “rising” and “falling”.
In regards to the mind, if thoughts arise during meditation, one should acknowledge them as “thinking”. It doesn’t matter whether one is thinking about the past or future or whether one’s thoughts are good or bad; instead of letting the mind wander and lose track of reality, bring the mind back to the reality of the thought with, “thinking”. Then return to the rising and falling and continue practice as normal.
In regards to dhammas, when the mind gives rise to liking, pleased by a certain experience, create the clear thought, “liking, liking”. When disliking arises – anger, boredom, frustration, etc. – create the clear thought, “disliking, disliking”, “angry, angry”, “bored, bored”, or “frustrated, frustrated”. When laziness or drowsiness comes up, create the clear thought, “lazy, lazy”, or “drowsy, drowsy”. When distraction or worry arise, “distracted, distracted” or “worried, worried”. When doubt or confusion arise, “doubting, doubting” or “confused, confused” and so on.
Once the above hindrances subside, bring the mind back again to a clear awareness of the present moment by focusing on the rise and fall of the abdomen.
The 16 steps or stages of anapanasati: