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)

131. 12. So, then, because the church comes from the Lord, conjugial love comes from Him as well. Because this follows as a consequence from what we have already said, I refrain from confirming it further. Besides, the angels of heaven all testify that truly conjugial love comes from the Lord; and they testify also that this love depends on the state of their wisdom, and that the state of their wisdom depends on the state of the church in them. That angels of heaven testify to these points is apparent from the narrative accounts at the end of the chapters, which are things I saw and heard in the spiritual world.