@digger, my T brings this up ALL the time. Some days I wonder if he's just trying to see what it will take to get me to throw something at him from across the room. So, now I'm wondering if this a part of the whole PTSD deal, rather than just him, picking on me.
What he says is that everyone needs a "reason to get up in the morning". He has told me (often) that the vast majority of the time, by the time his clients conclude their therapy, they have reached to point where they believe that that reason is "loving and being loved". He says it doesn't have to be people, although often if is. It can be anything, a cause, your car, your garden, but something.
It turns out, I have some kind of "thing" about the word "love". Apparently it's a "trigger" for me. The word, mind you, not the emotion so much. So, typically, when he throws that out that, I launch into a tirade about how ephemeral and undependable love is. And he listens, patiently. I don't have an answer. Just wanted to say I'm familiar with the question. I tend to look for the answer in the category of "dedication to some cause bigger than myself." But, since I do believe in God, I figure, if I'm still here, it means he's not done with me yet and I should probably hang around to find out what that means.
I'm both sorry you haven't found the answer to this question and glad you brought it up! Maybe it's not so different from the "Why are we here?"questions that philosophers have been debating for centuries. And, maybe, a lot of "normal" people never have enough reason to examine their lives, and their meaning, so they live unaware of the question.