Shame
Let's go back to the beginning. The beginning of God's creation. After six days of creation, 'God saw that all that He had made, and behold, it was very good" (Genesis 1:31). Now at the end of Genesis 2, following the account of Eve's creation, God tells us that Adam and Eve "were both naked and were not ashamed. (Genesis 2:25).
Satan entered the picture. He tempted Eve to eat the fruit of the one tree to which God had forbidden them access. Eve then gave the fruit to Adam and he ate it. At that point several things changed, but one in particular, their eyes were opened and "they knew that they were naked" (Genesis 3:7). The knowledge of their nakedness brought something else into their lives. Shame.