Genesis 2:25: And they were both naked, the man and his wife, and were not ashamed.
Revelation 3:17: Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked:
Before the Fall in the Garden of Eden, Adam and his wife were naked and did not know it, for there was a holy veil upon them, and that veil of holiness was the Glory of God that shone forth from within them and which robed their bodies (please read Robes of Glory before the Fall). When Adam and his wife eventually fell, then the veil of holiness left them, so that they looked upon each other and saw the naked form of their bodies.
In the last days, a similar situation has happened. The people are naked (they are not robed with the Spirit of God upon their soul) and do not know it, for Satan has put a lust veil upon the people, so that they do not even know that they are sinning. Satan made sin glamorous, he made it fashionable. He made a better world to sin in, and the people sinning do not realize their state because of the perverted veil on them.
When the veil of holiness left Adam and his wife, then they realized their naked condition and quickly ran away in order to hide themselves from the presence of God (Genesis 3:8). And so under the sixth seal in Revelation 6:12-17, when the Great Tribulation sets in, the lust veil upon the people will be lifted, and they will realize their sinful condition, and will run to hide themselves from the wrath of the Lamb.