Strawberry
A Buddhist monk was being chased by a hungry tiger. The tiger chased him right off a cliff. The monk caught a vine on the way down. The vine held, barely. It was a long drop to the rocks below, certain death. Then a mouse began to chew on the vine, out of his reach.
The monk sees a strawberry growing out of the cliff face where he is hanging. He picks the strawberry and eats it.
He says "This strawberry is delicious!"
The past is gone, never to return. What you had for lunch yesterday is every bit as gone as Charlemagne. Irretrievable in the absolute. The future is an illusion. The old riddle goes, "What is always coming but never arrives? The future." There is more truth to that than you might suspect. It's not just a word game. The future is nothing real. Now is the only time that is real, and now is in constant change. The future is only our anticipation in the now of further changes -- that the now will continue to change.
How sad to let changes that are not yet happening ruin the now.
This is not to say we should not plan for the future. The future is a useful metaphor, but it is just not anything real. So I guess what it means is "don't worry". If you know a bad thing is going to happen, prepare for it, but worrying never does anyone any good. Don't worry. Enjoy the now and deal with whatever is impending when the now becomes it.
Realizing the future is really only an idea, makes me think time travel to the future will never be possible for the simple reason that you cannot travel to a place that does not exist. Bummer.