I shall assume that morticians can derive more hope than from the thought than most can. But the rest of us need to mitigate the perceived futility of life, death, action, creation and destruction by remembering what makes something valuable in the first place, and by conquering the fallacy of thinking that the future perspective is always the clearest and most correct.
Let me refer, once again, to the idea that nothing has value except in being experienced (or having its effects experienced) by a sentient being.1 The value of anything you do or make is measured (approximately) in its benefit to sentient creatures (whether in utility, aesthetic appreciation, or pleasure). Therefore, the perspective from which to judge something's value is within the time (and space) in which it is being appreciated.
If I make a drum, and it provides people with enjoyment for thirty years before getting broken, I will not afterward regard the effort as having been wasted. The fact that it created some happiness cannot be taken away. Once the planet becomes uninhabitable2, the former existence of the drum will be meaningless. But that perspective is nobody's perspective, so it is a rather silly one to take. My perspective is based in a time when the things I value (such as people) exist. And within this (more useful) perspective, the drum and my work retain their significance.
The tempting fallacy comes from overextending something that we generally assume to be true: "Hindsight is 20/20." Many things looks clearer, more cut-and-dried, from the perspective of the future. However, the passage of time frequently fails to improve our perspective. People and societies forget. Records, artifacts, and even values are lost.
Flashing forward to a time when everything we know is dust, we do not gain the improved perspective that the "future" promises; we gain no perspective at all.3
So live for what will be in your lifetime; it is the most important (and only) time you will have.
1. See "Does a dog have Buddha nature?"
2. In, say, seventy years.
3. At least, no human perspective. A universal perspective, in which nothing matters, can occasionally be useful to mental endeavors such as meditation or seeking oneness with the universe, and may be sought in this way.
