You don't have to finish it. All those things you could do, all those things you should do, all those things you want to do -- you don't have to finish them all. And you won't. When you die, as you will, there is so much that you will leave undone, incomplete, unfinished. And that is fine, that is not only normal but inevitable, that is the way of the world, and you share that in common with all people in all places and times.
You don't have to finish it. And you also don't have to see your life as one small step in a long chain from point A to point B, a milestone against some arbitrary measuring stick in an inexorable march of progress from what was, to what will be. That is not how the world works. Times rise and fall, empires rise and fall, fashions and moral codes and religions and schools of thought rise and fall, and if you do not see "progress" in your own particular lifetime, that is okay. Do what you can, what you are called to do, and that is enough. Some cycles, perhaps most cycles, play out in decades, centuries, eras, and some cycles, perhaps most cycles, are not even obviously cycles at all. Humanity projects a need for simple rules, narrowly-defined forward progress and easily understood patterns onto a universe which is so much richer, so much more complex than that. The universe is far more vast, more wonderful, surprising, and full of mystery than we can possibly imagine.
You don't have to finish it, and you won't. You don't even have to make progress, and you may not, depending on your own definition of progress. All you have to do is let go of the fear, and live your own life fully and completely. With passion and fervor, engage the world around you and those in it, and do what is in your heart to do. Love, live, and create, and know that the trajectory of your life, the words you speak, the thoughts you have, the lives you touch, and most especially, the love you bring to the world, these are the impressions you make onto the essence of the cosmos itself. These wonderful tracks made as you walk, your life's true Tales, they never fade, do not age, do not pass away, they are forever and always part of the eternal fabric of the universe, for all time, as long as time shall be. This one truth is a thing so true that all the universe stands in quiet witness to it, now and forever.
You don't have to finish it. And you don't have to make progress. You have a life, and a death, a beginning and an ending. And in between is magic, that is your birthright: to live your life as fully as you can, and have your own unique Tale become a part of the grand weaving which is constantly creating the universe -- an essential piece of the great infinite story which tells itself, the song of all voices which sounds everywhere, in all places, creating and reifying existence, at every moment, sung in love and beauty by every speck of matter and energy that was, is, or shall be. You are not merely a meaningless letter upon a page, you are not a single word in a sentence, you are not a sentence in a paragraph, a scribbled footnote, or even a single page in the book. Your life is a dense, rich chapter, a whole section, one entire book in a series, full of richness and meaning, and the loss of a chapter, or an entire book, leaves a gap that no one else can ever fill.
But you don't have to finish it, because there is no "it" to finish. You don't have to make "progress," because your entire life is progress enough. You don't have to worry if you are doing enough, or if you made the right choices, you don't have to second-guess your own life. By the standards of the universe, you are already a success, and the proof of that success is your very existence. Just as you cannot escape your life, your life cannot escape you.
You don't have to go out and write the book of your life, because you are writing it, in every moment, through every action, every choice, every word, each creation, touch and love. Your living history, the song of your life, the story of who and what you are, and your place in the great Tale, is being told all around you. There are no bit players, no anonymous actors, no unimportant stories. All voices are heard, and all tales are told.
So you will leave things undone. And yet, your Tale will be complete in itself -- not a fragment, not an unfinished story, but complete, entire and perfect.
So relax, open fully to the wonders of the universe, drink deep of the exquisite joys and precious pains and love and laughter and sorrow and agony, immerse yourself in the communions and loneliness and rapture and boredom and wonder and mystery. Know that who and what you are, your life, however long it lasts, will be complete, and that your Tale, whatever it is, matters, and that your life has meaning, even if that meaning is not clear. The fact that you are here is mystery enough. Your existence itself is such an incredible, improbable miracle that to question its worth is very much the same as questioning the worth of the universe. It is, and you are, and that is mystery and meaning enough to ponder for one lifetime, or many.
Breathe, live, and love. That's all you need to do. And look, you're already doing it. That's all there is to it.