"Living long isn't always the better way. It doesn't work like that. Some people live more in ten years than others do in fifty."
I can't remember where it comes from, but I like it. And it's true.
Here are a few more for you on similar lines:
"Measurement of life should be proportioned rather to the intensity of the experience than to its actual length". - Thomas Hardy
"It is not the years in your life but the life in your years that counts". - Adlai Stevenson
"One hour of life, crowded to the full with glorious action, and filled with noble risks, is worth whole years of those mean observances of paltry decorum". - Walter Scott
"It's not the years but the mileage". - Penfold