Your meditation guide outlines a very practical and effective sequence, and your reasoning for the order of these "four powers" is spot on. The method is a beautiful example of how preparing the body is a crucial first step to calming the mind.

Here's a breakdown of why this sequence works so well, based on your description:

1. Posture First: Shoulders and Jaw

You begin by addressing the physical body, specifically the areas that hold a lot of subconscious tension: the shoulders and the jaw.

• Why it works: Physical tension is a major distraction. If your shoulders are hunched or your jaw is clenched, your nervous system is in a state of subtle alarm. This makes it incredibly difficult to focus on something as subtle as the breath. By relaxing these areas first, you're not just improving your posture; you're sending a signal to your brain that it's safe to calm down. As you noted, a good posture is an essential "environment" for the meditation. Trying to focus on the breath with a tight, uncomfortable body is like trying to listen to a whisper in a noisy room. You must quiet the external noise—in this case, your physical tension—first.

2. The Breath: In-breath and Out-breath

Once the body is relaxed and stable, you can shift your attention to the breath. This is where the core of the meditation practice begins.

• Why it works: You can only fully surrender to the rhythm of the breath once the body is at ease. The physical relaxation from the first two steps allows you to take a full, deep in-breath that isn't constricted by a tight chest or neck. This deep breath further activates the body's relaxation response. The focus on the out-breath and the subtle sensation around the voice box is a brilliant anchor. It gives the mind a precise point of focus, which is necessary to prevent it from wandering. This gentle "pushback" provides just enough of a physical cue to keep you present without requiring effort that would re-introduce tension.

3. The Return: A Continuous Loop of Awareness

You highlighted a key part of the practice: the act of "returning" to the body. This is a powerful, often overlooked, aspect of meditation.

• Why it works: Your mind will inevitably wander. That's a natural part of the process. The "four powers" don't end after one cycle; they form a continuous loop. As you focus on the breath, you periodically check back in with your posture and jaw. This constant, gentle self-correction keeps you from falling back into old habits of slouching or tensing up. This "returning" isn't a failure of the practice; it is the practice itself. It’s the constant, gentle act of bringing your attention back to your body and breath, which strengthens your mindfulness over time.

This method starts with a physical foundation, moves to the breath as a primary focus, and then integrates a continuous loop of awareness. The combination of these steps—first relaxing and stabilizing, then focusing and surrendering, and finally consistently returning—is what leads to the state of calm and clarity you described. It's a holistic approach that acknowledges the interconnectedness of the body, breath, and mind.