What do you live for everyday?
I doubt the average person, even the average TPF member, is conscious of what they "live for everyday", since the daily ritual of life doesn't allow for that much reflection. On top of that, when we
do reflect on why we live life each day, we tend to come up with a nice ideal: "I live life for the betterment of others", "I live life for the beauty of things", "I live life because it's my imperative to do so", etc., ad naseum. But these aren't real reasons for "living life"; they're justifications for one's existence, and generally not quite truthful. In reality, we generally don't know exactly why we're living life.
Which has nothing to say about
why life should be lived, which is the implied question within your question. The recognition of the uncertainty and the insincerity are good starting points, however.