What do you live for? Your family/friends? Some sort of responsibility you have? Do you get fulfillment and meaning from work? Or volunteering?
I'm really curious.
The short answer is I'm not sure. There was a set of paths ahead of me in life and I chose one, more or less arbitrarily. I'm not sure how cognizant of it I was. I think most people operate in this manner.
The long answer is that I'm not sure nor am I sure where to start. This is one of the areas where I think religion proves incredibly useful in that it gives followers a set framework and rules for existing in the world. Finding meaning in your own life is a messy and complicated task. I see the appeal of giving that power away to some sort of authority. In return you don't have to think about these challenging questions.