I have two such axioms that have shaped my entire Camino existence and experience since the first go:
"I have come to learn that the the journey IS the destination..."
(Anonymous - But I have this one framed in my home - a gift from my wife after my first Camino. She heard me say it several times on phone calls and in e-mail messages back and forth. I cannot claim credit for originating this one, but is is very true.)
"On any day, remember that there are days to be brave, and days to be smart..."
(Tom A. (me))
There is another, which is told in several forms. Here is my version...
"The Camino, any camino is simply a long walk. Some are arguably longer than others. A Camino is comprised of many individual steps. One merely takes a step, then repeats that process, known from infancy, about one-million times. Just remember to stop when you reach the Cathedral in Santiago..." (Anonymous)
Or my (coined this year) "Finisterre Route" variant... "Turn right at the corner at the end of this block, and stop walking when you come to the ocean...in about four days..."
(Tom A. (me), 2016)
Finally, there are the unofficial Camino Rules:
1. Never judge another person (or their Camino, gear, companions, behavior....) lest you be judged;
2. The Camino provides (it really does you know);
3. Saint James works in strange ways (sometimes in VERY strange and even weird ways);
4. Always treat others you encounter the way you would like to be treated;
5. Always help another pilgrim in need; and
6. Pay it forward (the good deed is it's own reward), encourage others to do the same.
The first three or four axioms are very well known on the Camino. I am not aware that anyone has formally coined the unofficial "Camino Rules" anywhere. If you find them, please share them.
I added the last two are from my own experiences on Camino. I found them to vastly improve the quality of each day, at least for me.
It did not matter if it was a kind word, a willing ear, a shoulder to cry on, first-aid treatment, sharing snacks or a meal, bottled water, or a ride, scrounging in a donativo box, giving away gear excess to my needs to another pilgrim I came upon, or even buying needed gear at a store for another at my expense, it did not matter. I am blessed to be able to offer encouragement, assistance or more tangible help, so I do. This is my nature. It comes to me naturally. I am also known along the Camino and in Santiago by this behavior.
In fact, I have come to realize that unless I can find other pilgrims to interact with and help if needed, my day is not complete. It is one reason why I did not like the Madrid Route this past April (too few pilgrims), and another reason why I so love working as a volunteer at the Pilgrim Office in Santiago (lots of pilgrims).
I hope this helps.