People say it all the time. Life is short. The years go fast. You hear it at birthday parties, in passing conversations, from anyone watching their kids grow up a little too quickly. It has become one of those observations so common that it no longer sounds like much of anything.
Strange, then, that the quote at the top of this piece — one that pushes back on exactly that feeling — comes from an essay titled On the Shortness of Life. He observes that many people complain about life’s brevity — and then argues they are wrong. “It is not that we have a short time to live,” he writes, “but that we waste a lot of it.”
I came across Seneca a few years ago during a stretch when I was reading everything I could find on Stoicism. It was a period of failure, and of looking for something that might make sense of it. I read Marcus Aurelius, I worked through the other classical texts, and this is one of lines that really stuck and I have continued to think about.
Let’s run the numbers for a moment. According to the CDC, US life expectancy hit a record high of 79 years in 2024. That is roughly 28,800 days. Assume eight hours of sleep a night and you get somewhere around 460,000 waking hours across a lifetime. If you are 35 right now and live to 79, you have close to 255,000 of those hours still ahead of you.
That is not a short supply. The problem, if there is one, is probably not the quantity.
So why does it feel short? Why does everyone over forty say the years are accelerating?
It seems part of the answer is structural. Associate philosophy professor Iskra Fileva at the University of Colorado Boulder notes: “a year in the life of a 6-year-old is 1/6th of the child’s life, but in the life of a 60-year-old, it is 1/60th. That matters.” A year feels enormous at six because it represents a huge proportion of everything you have ever experienced. At fifty, the same twelve months barely register as a fraction.
This is probably why childhood felt so long. Not because more happened in a literal sense, but because each year was a bigger piece of the whole.
But the deeper mechanism might be newness. Research fellow Marc Wittmann at the Institute for Frontier Areas in Psychology writes: “The more novel and fulfilling experiences we have, which we attend to with more interest, the more memories are built. This enhanced memory formation leads to the feeling that life has lasted longer.”
Childhood is packed with firsts. New school, new teachers, things you can do this year that you could not do last year. The brain has a lot to work with. Adulthood, when weeks start looking identical to other weeks, collapses in memory. Time does not speed up. It just stops leaving marks.
I got a version of this firsthand. My first year living in Vietnam felt enormous — longer in retrospect than most years since, despite being objectively the same length. Everything was new: the city, the noise, the food, the language I was slowly piecing together, the version of myself I was becoming. Memory had material. Time expanded because experience was dense.
The years where I have let routine take over without much variation have compressed. I say this not as a complaint. I say it as a clue about where the feeling of “not enough time” actually comes from.
I don’t think Seneca was offering reassurance. I don’t think he was saying “you have plenty of time, don’t worry”. His point was more uncomfortable than that: the feeling of running short on time is largely a consequence of how the time was spent, not a fixed feature of a human life. Wasted time does not just disappear — it becomes, in memory, as if it never happened at all.
“It is not that we have a short time to live, but that we waste a lot of it.”
The question isn’t where the time went. It is what we were doing with it.