The poem 
by Antonio Machado where the phrase we make the road by walking comes from, says "caminante, no hay camino, se hace el camino al andar". Though one translation of this is "we make the road by walking", there are other equally valid translations.
Another important phrase in the poem says "upon glancing back one sees the path that must never be trod again." The idea of the unavailability of the path for retravelling is further compounded by the last line of the poem, which says "caminante no hay camino, sino estelas en el mar" or "walker there is no path, just wakes in the sea". The path is not permanent, it fades like a vapour trail...
The poem seems to suggest that we shouldn't overstate the importance of the given path, over the practice of walking that changes the path every time.
Further related reflection about these ideas at Camino de Santiago and Tell a Passing Stranger