Well, this is tough on multiple levels. But apparently the Greeks did not diet.
You aren't bothered, are you, because you weigh a certain amount and not twice as much? So why get worked up that you've been given a certain lifespan and not much more? Just as satisfied with your normal weight, so you should be with the time you have been given.
Yeah, but what if you ARE bothered by your weight? Oddly, I am not nearly as worried about my life span as much as my weight. So let us turn to Seneca, which puts it better.
Life is long, if you know how to use it.
So let's summarize for modern times. The length of your life is unknowable, but the quality and enjoyment of that life is up to you. To put this in perspective, the Greeks worked as little as possible. They believed that contemplation, enjoyment and play were the real meanings of life, and work was just a way to get what you needed.
It was with Christianity in particular that pushed the idea of a "work week" and how work as a signifier of good morals became the norm. Of course, much of the output of that work, the wealth, was transferred to the church and local leaders. The church in particular was one of the first institutions (as opposed to individuals) that turned our output into their wealth.
That lesson has been learned and redoubled by corporations and a "Protestant Work Ethic" that has warped our sense of self to honor a belief that what you earn and your criticality to your company are the ideals to strive for. And, not achieving them means your are less than your peers. And rejecting that principle of work is even more disgusting to your countrymen than becoming a non-believer was to your community 500 years ago.