Read the passage below from "a celebration of grandfathers" by rudolfo anaya and answer the question that follows.

real life takes into account the natural cycle of growth and change. my grandfather pointed to the leaves falling from the tree. so time brings with its transformation the often painful, wearing-down process. vision blurs, health wanes; even the act of walking carries with it the painful reminder of the autumn of life. but this process is something to be faced, not something to be hidden away by false images. yes, the old can be young at heart, but in their own way, with their own dignity. they do not have to copy the always-young image of the hollywood star.

what does the expression "the autumn of life" refer to?