Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. These straight paths are called geodesics. Like Newton's first law of motion, Einstein's theory states that if a force is applied on an object, it would deviate from a geodesic. For instance, we are no longer following geodesics while standing because the mechanical resistance of the Earth exerts an upward force on us, and we are non-inertial on the ground as a result. This explains why moving along the geodesics in spacetime is considered inertial. (wiki)
Over the last three years I've been getting further away from a systematic curriculum. My own practice has changed so profoundly and is so exciting that I have been unable to contain myself. The illusion that the earth is pulling us down causes us to seek power and to use structure and effort. Cause is hard to assess, the "cause" of illusion may simply be desire followed by aggression, followed by deficiency...that would be the daoist take in a nutshell. But see through the illusion which creates the need for structure and profound changes start to happen.
Try this active spacial mind thought experiment: You have a 8"x4" inch by 7' foot long plank on your shoulders, you are moving in a crowd and you don't want to bonk anyone. Reduce the force in your feet to zero.
An alternate version of this experiment is: Imagine each of your 10 fingers are touching someone's closed eyes and you don't want to hurt them. Zero out your feet.