Listening now, it's a good one -- but there are actually more than three stages, even though on a shorter Camino such as one from SJPP those are very often the three that you will experience.
We do of course have a strong tendency as human beings to organise ourselves into ternary structures -- and that is excellent and natural, so that the typical structuring of people's pilgrimages into these three stages has a great deal of truth in it.
The easiest stage to explain outside these three is what I call "stage zero" -- it's the immediate experience of the first few days (or week) after you walk out from home, if you start from there, beginning in the very familiar and slowly walking out and into an incrementally increasing degree of unknown.
The initial four stages in my 1994 from Paris were 1) zero 2) mental 3) physical 4) spiritual -- and that was all before I had even reached SJPP.
I do not understand all of the stages beyond those, and I think there are some I still need to discover -- but there's a shocking "sudden crowd" stage, an "alone in the crowd" stage, a "back home, now what ?" stage, an elusive "religious" stage. And a VERY difficult "suddenly alone again" stage if you've been walking among others, but then find yourself completely solitary, the only pilgrim on your Way, with not even one hospitalero to help and understand.