To eat from the tree of knowledge of good vs. evil. This was the fall from grace. Consider this: Eden was as imperfect as the world we live in now. It was only after Adam and Eve ate the fruit from the tree of knowledge of good vs. evil that they were able to label things good and bad. Prior, things were as they were, imperfect, but imperfection was completely accepted, and therefore, Adam and Eve were at peace and stood in the grace of God. As soon as their minds latched on to the notion that things should ONLY be good, they fell out of grace and were no longer at peace.
“There is nothing good, nothing bad; thinking makes it so. All is God. In the worst there is God; in the best there is God. Beyond God there is nothing.” Yogi Bhajan
The goal of yoga? To be at peace, to stand in the grace of God DESPITE being imperfect and living in an imperfect world.