Physiologicaly? No freaking idea whatsoever. Nor does it matter.
Here's what it is: knots. Tied knots. Lots of them. And you are constantly tying more. You're like Gulliver, tied down tightly to the ground with tons of little pieces of string. And you're the one doing the tying and always have been.
Everything you grab at, every goal you attach to, every time you fall out of love with the world as it is in this moment and need to make things just right, you are tying a knot. And you've been doing it for a long time (the Hindus say thousands of lifetimes). So you are locked up absolutely tight. You have no idea how tight. If you practice diligently and the knots start to loosen a little, you'll feel nothing but compassion at the observation of an entire world of divine beings getting themselves more and more snagged and bound and imprisoned, all of their own volition. It's surreal.
Those reading along may believe they have an intuitive understanding of what I'm saying. I thought I understood it, too, for years. Then I got into a very diligent meditation practice, and actually experienced the loosening of the knots, and I know I knew nothing. For one thing, it's not a metaphor. But don't take my word for it...find out for yourself!
