"From around the age of six, I had the habit of sketching from life.
I became an artist, and from fifty on began producing works that won some reputation, but nothing I did before the age of seventy was worthy of attention.
At seventy-three, I began to grasp the structures of birds and beasts, insects and fish, and of the way plants grow.
If I go on trying, I will surely understand them still better by the time I am eighty-six, so that by ninety I will have penetrated to their essential nature.
At one hundred, I may well have a positively divine understanding of them, while at one hundred and thirty, forty, or more I will have reached the stage where every dot and every stroke I paint will be alive.
May Heaven, that grants long life, give me the chance to prove that this is no lie."
For the record he did live to 88, which is a bit more than double my age (almost triple the original poster's age).
I don't think he believed he would live to 150, but saying that expressed his feeling of something that was beyond his reach but which animated every moment of his life and his art.
What I take from the quote is that existence shouldn't be a bell curve, with half or more of your life as an inevitable decline, but that your youth can be a foundation upon which to build knowledge and wisdom. You should end up smarter after many years, shouldn't you?
To be able to look back and smile at one's bravado, knowing that you can do so much more now, with less effort and rush, and that if you continue striving, you'll do even more in the future. To deeply and truly understand your craft.
That's what I'd want, a real life worth living, not to be the tech equivalent of a child star.
If you find that you are declining mentally after 30 or 40, you are either doing something wrong or are genetically extremely unlucky.
Exercise, a good diet, proper sleep, combined with plenty of intellectual and social interactions seem to be enough to keep you from measurably losing any mental faculties well into your 70s or 80s (and even 90+ if genetically lucky).
It actually is inevitable, as even you admit when we begin to reach our 70s/80s ;). If we don't die of something else, all of us will die of Alzheimer's. Simple fact of universal amyloid plaque buildup. http://www.amazon.com/Ending-Aging-Rejuvenation-Breakthrough...
Also technically incorrect on the mental decline as well - our brains do start to irrevocably decline at around age 30. Our myelin sheaths fully develop in the early 20s, and from there, we have a few golden years until it's all downhill :D http://www.sciencedaily.com/releases/2009/03/090320092111.ht...
I find encouragement in the quote by the painter of "The Great Wave off Kanagawa", Katsushika Hokusai:
http://en.wikipedia.org/wiki/Hokusai
"From around the age of six, I had the habit of sketching from life.
I became an artist, and from fifty on began producing works that won some reputation, but nothing I did before the age of seventy was worthy of attention.
At seventy-three, I began to grasp the structures of birds and beasts, insects and fish, and of the way plants grow.
If I go on trying, I will surely understand them still better by the time I am eighty-six, so that by ninety I will have penetrated to their essential nature.
At one hundred, I may well have a positively divine understanding of them, while at one hundred and thirty, forty, or more I will have reached the stage where every dot and every stroke I paint will be alive.
May Heaven, that grants long life, give me the chance to prove that this is no lie."