Interiorization as a way to a deeper practice

Why do we start our practice always with focusing on some particular things like air temperature, sounds, breath, etc.?

In his teachings Patanjali calls this interiorization, which is a shifting of perspective away from externality toward an interiorized point of view.

More specifically, interiorization is the growing sense that awareness is not seeing an object per se but instead observing a consciousness representing an object.

During the systematic practice of stilling (nirodha), interiorization usually begins to arise when we lock our attention on a single object or field (dhāraņā). As the senses spontaneously cease to react to external stimuli, a phenomenon Patañjali calls pratyāhāra (2.54), consciousness begins to grow calmer and more refined in its perceptions, and capable of noticing the ordinarily invisible movements of consciousness itself.

The experience is something like viewing a realistic image in a painting at the far end of a gallery. As one comes closer, the brushstrokes and the texture of the canvas become visible-eventually to the point where the image has completely deconstructed and can no longer be seen unless one elects to step back.

In our practice interiorization helps making practice for refined, more focused and intentional.