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)

9589. There is heavenly freedom and there is hellish freedom. Heavenly freedom consists in being led by the Lord; and this freedom is the love of goodness and truth. But hellish freedom consists in being led by the devil; and that freedom is a love of evil and falsity, or a craving, strictly speaking.