Imagine that you'll be dead in a minute. You know with 100% certainty that this is your last minute running to its end.
Would you rather regret not spending this last minute on something else or be grateful for what you've got?
Most people follow the regret road. But if we think a priori that happiness is what we're after in life, then regret path doesn't make much sense. It won't make you any happier. And what's the point of being anxious about the future if you'll be dead in 45 seconds?
But we live our entire lives like that. We're always worried about money, relationships, sex, career, and a bunch of other stuff yet to come.
What's worse, we worry about these things right when we can't do anything about them. We're having dinner with a loved one, but our thoughts are at work, trying to solve this problem we have to crack by Monday. We're taking a morning stroll, but our mind is still going over that quarrel with mom last night.
As a result, we're not living our lives that much. We're not present. But we feel it's okay because these problems we worry about seem important. And because we know with certainty that we'll wake up tomorrow morning.
But nobody knows how much time we have left.
There's a non-zero chance that this is actually your last minute coming to its end. Take a few seconds to think about this. If you're a 23 y.o. male like me, you have a 1 in 680 chance of dying in the next year and a 1 in 248,176 chance of dying tomorrow.
It doesn't mean you need to become a monk and drop it altogether. But it's so much wiser to enjoy the experience you're having at any given moment instead of being anxious about the future. To be present and give your full attention to things. To live each moment like your last. Because the future you're so worried about may never come.