What is your purpose... your meaning... your thing that drives you forward through life?

I find the notion of purpose and meaning to be necessary for a sane and 'productive' life. Without a major traumatic emotional event, however, I don't see how any human could dedicate his life to one endeavor. I come from a christian background, but I've renounced religion because muh rationality. This way of looking at the world has only brought me misery, because it has deprived me of any meaning.

I want to live. Indefinitely. But at the same time I find no reason to live.