What is the theme or lesson of Santiago carrying around his jacket and how does the jacket embody or symbolize that theme?

Coelho's
is a symbolically rich tale. Most of the symbols are explained in one way
or another. The jacket doesn't seem to be one of the many Christian or Arabic symbols, though.
It seems merely to be an item of clothing. The jacket first appears on the first page of the
book as Santiago uses it not to get warm, but to sweep up his resting spot under the broken roof
of the abandoned chapel. This opening scene is set in summer when the boy is annoyed that he has
to carry his jacket. But then he...