On paper a circle is but a rotating triangle.
The tip of the triangle has two sides that we can think of as left side and right side.
If we try to stand on the tip of a triangle and we lose our balance then we will fall off to either the left side or the right side.
Thus, in controlling the ring any part of the circle can instantly be considered the tip of a triangle. Refer to page 113 of TaijiKinesis Vol 2 for the conceptual drawing.
Page 119 Section 8.7 (b) of TaijiKinesis Vol 2 is the very first thing we must learn in order to master our neutralization skills. If you don’t get this down pat then you can expect not to be able to defend your space each time you play push hands.