The answer to the question "What is the meaning of life?" is elusive for at least two reasons. The first is obvious: there is no one meaning. What life means is up to each individual to determine. But more importantly, it's elusive because people tend to look for it where it does not exist–in the future.
Life does not gain meaning from things we haven't done, but from what we have left behind. For example, over the past 25 years or so, I've edited a lot of books. Probably at least 100, I 'm terrible at keeping track. Those books are among the relics of my life. They are things that would not exist, at least not in their present form, without my life.
For me, the books are things no one can take away. Even if I developed Alzheimer's disease and forgot that I had ever edited a book, those books would still exist. Even if all books were banned and burned, they will have still affected those who read them–helped with a research project, answered a question–and so part of the meaning of my life lies there. And of course the books matter hardly at all compared to the impact my life has had on Kate, Maggie, Ellen, and all of my other friends and family.
I'm also beginning to realize the importance of gratitude. Generally I'm grateful for things I have in what I think of as the "near-present," because the "present-present" doesn't exist; as soon is it is here, it is past. I've been grateful for things I anticipate, such as getting a new job, or things in the past, but I think most of what I appreciate is in the near present–a place to live, running water, good health. Being grateful and remembering the things no one can take away helps me be more focused in the near-present where life is happening.
And what about those who truly believe, after carefully and honestly considering every moment of their life, that they have nothing that no one can take away, nothing to be grateful for? They may be capable of the most important gratitude of all: gratitude for having nothing to lose.