Our lives are lived in constant possibility, pregnant with options. We are limited only by our beliefs, self talk and fears.
We are not given a limited supply of life force at birth that runs down as we age. When I think of this idea, I see the aged Buckminster Fuller jumping up and down on stage filled with enthusiasm (I was privileged to see and hear him several times). Or I remember Dr. Joseph Murphy rapidly talking with zest in his later years. There are quite a few examples just in my personal experience. My age is no excuse for not participating fully.
If we believe all is lost, for us it is. If we believe there is no hope, for us there is none. We set the limits of our lives ourselves. There are countless examples of overcomers strewn across history. They are our heroes. So I suggest - be your own hero.