Darn good question, and you have an eloquent way of asking it.
In my older days, it was fear, and fear of failure.
It served me well in some ways, but what a price to pay.
For me, it's a combination of things, such as exploration, paradox, and boredome at times. I like to have things to look forward to.
I like to see my family grow and be happy.
There is also a bit of AA in there. I believe in a higher power, I myself call him God. I try to have some faith that he ultimately has all power, I'm just a teensy little thing, only on this earth for a short time.
I really believe the fear thing is gone, none that I'm consciously aware of, for which I'm gratefull.