The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.

(References: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)

9586. Doing what is bad, when one loves and delights to do it, seems like freedom; but it is slavery, because hell is the source of it. Doing what is good, when one loves and delights to do it, also seems like freedom; and it is indeed freedom, because the Lord is the source of it. It is slavery therefore when a person is led by hell, and freedom when a person is led by the Lord. This is something that the Lord teaches in John,

Everyone committing sin is a slave of sin. A slave does not remain in the house forever; the Son remains forever. If the Son makes you free, you will be truly free. John 8:34-36.