Leaving that issue aside, let me return to the smaller-scale dimensions of human life. Even if life as a whole is meaningless, perhaps that's nothing to worry about. Perhaps we can recognize it and just go on as before. The trick is to keep your eyes on what's in front of you, and allow justifications to come to an end inside your life, and inside the lives of others to whom you are connected. If you ever ask yourself the question, "But what's the point of being alive at all?" -- leading the particular life of a student or bartender or whatever you happen to be — you'll answer "There's no point. It wouldn't matter if I didn't exist at all, or if I didn't care about anything. But I do. That's all there is to it."
Some people find this attitude perfectly satisfying. Others find it depressing, though unavoidable. Part of the problem is that some of us have an incurable tendency to take ourselves seriously. We want to matter to ourselves "from the outside." If our lives as a whole seem pointless, then a part of us is dissatisfied -- the part that is always looking over our shoulders at what we are doing. Many human efforts, particularly those in the service of serious ambitions rather than just comfort and survival, get some of their energy from a sense of importance — a sense that what you are doing is not just important to you, but important in some larger sense: important, period. If we have to give this up, it may threaten to take the wind out of our sails. If life is not real, life is not earnest, and the grave is its goal, perhaps it's ridiculous to take ourselves so seriously. On the other hand, if we can't help taking ourselves so seriously, perhaps we just have to put up with being ridiculous. Life may be not only meaningless but absurd.
Thomas Nagel, What Does It All Mean?: A Very Short Introduction to Philosophy (1987), Ch. 10. The Meaning of Life