Here is a quote from Roman philosopher Seneca's On the Shortness of Life, a 2000-year-old treatise on how we spend our time that still rings true today.
Photo by Ryan Baumann.
It is not that we have a short time to live, but that we waste a lot of it. Life is long enough, and a sufficiently generous amount has been given to us for the highest achievements if it were all well invested. But when it is wasted in heedless luxury and spent on no good activity, we are forced at last by death's final constraint to realise that it has passed away before we knew it was passing. So it is: we are not given a short life but we make it short, and we are not ill-supplied but wasteful of it... Life is long if you know how to use it. -- Seneca, On the Shortness of Life
What It Means
This quote is pretty simple and straightforward. Seneca believes we have plenty of time in our lives to accomplish our goals, but instead we spend it on things that don't matter (Marcus Aurelius would call them "external things" or distractions).
By the time we're on our deathbeds, only then do we realise how much time we wasted. Only then do we see that life is not short, but that we chose to make it feel that way.
What to Take From It
We all want a fulfilling life. We want to do all the things, see all the things and leave our mark on the world. But in order to do that, Seneca says you must avoid "heedless luxury" and "no good activity", whatever that may be under your circumstances. In Seneca's eyes, your life will feel longer and more fulfilling if you're focused, vigilant and disciplined.
Now, this approach doesn't mean you should avoid the fun stuff entirely. You'd surely burn out and lose your mind if you did nothing but productive work. No, you need to change the way you look at your remaining time here. You need to see time as a finite resource that you spend and that you cannot earn more of.
Be careful and selective when you choose your activities. You should never be "wasting" time but "using" it. Sometimes you'll use your time for pleasure and sometimes you'll use your time for work, but never waste it. Spend your time here wisely and life will be exactly as long as you need it to be.
One of the main ideas Marcus Aurelius focuses on in his stoic writings is the notion that the mind is immune to all external things. For example, you can't control a situation's circumstances, but since they do not affect your mind, you can control how you react to them.