We certainly start to come to grips with our own mortality as we age. At 28, I'm having thoughts and concerns about illnesses I never thought I would, even though I'm certainly more aware of what I put into my body than I was just years ago.
I remember a conversation with my mom a few years back, where she started with something like "If I had died a few years ago." That was unfathomable to me because the thought of losing my parents is something I've always wrestled with and my mom is still very much youthful and carefree despite her advancing age.
Its a great piece that highlights the fact that at sometime we can and do come to terms with the fact that we won't be here forever. It's a sobering thought, but one that gives us perspective on life about the things that matter. In addition, realizing that we are mortal makes us want to leave behind a legacy, whether its a family, a product, or a book, we all want to be remembered for something.
I think we all come to this realization at different points in our lives.