There is a line that runs through every kind of growth: physical, creative, relational, financial. On one side is the comfort that keeps you small. On the other is the overwhelm that breaks you down. The Expansion Edge is the narrow band between them, where your system is challenged enough to adapt and supported enough to stay whole.
Most advice misses this. It offers two settings, force and ease, as if those were the only options. The truth is that the edge moves. On a strong day it is further out. On a depleted day it is closer in. Training capacity means learning to find your real edge today, the one you have now rather than the one a program assumes.
The 4Rs name the work plainly: Restore, Regulate, Rewire, Radiate. You restore the baseline, regulate the nervous system, rewire the pattern at the edge, and then the new capacity radiates into everything else. Skip the first two and the edge becomes a cliff. Honor them and the edge becomes a place you can return to on purpose.
This is why a generic plan fails most people. The plan does not know where your edge is. A real practice is calibrated, session by session, to the system in front of it. That is the whole game: find the edge, train it, let it move.