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)

In Micah 1:8, this signifies the grief of the angels of heaven and the people of the church.

In Jeremiah 25:36, this signifies that good and truth are vastated. (Arcana Coelestia 2240)

In Isaiah 23:6, this signifies grief on account of vastation. (Apocalypse Explained 406[11])

(References: Apocalypse Explained 695; Apocalypse Revealed 884; Micah 1; Revelation 21:4)