What is the misery of that estate whereinto man fell?

All mankind by their fall lost communion with God, are under his wrath and curse, and so made liable to all miseries in this life, to death itself, and to the pains of hell for ever.

Death is threefold:
First, spiritual death, the separation of the sinner from God.
Second, physical death, the separation of the soul from the body.
Third, eternal death, the abandonment of the soul in hell.

Genesis 3:8, 24 (ESV)
And they heard the sound of the LORD God walking in the garden in the cool of the day, and the man and his wife hid themselves from the presence of the LORD God among the trees of the garden...He drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life.

Ephesians 2:3 (ESV)
among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind.

Galatians 3:10 (ESV)
“Cursed be everyone who does not abide by all things written in the Book of the Law, and do them.”

Romans 6:23, Matthew 25:41 (ESV)
For the wages of sin is death...“Then he will say to those on his left, Depart from me, you cursed, into the eternal fire prepared for the devil and his angels.