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)

2877. Whenever the affection for truth and the affection for good are being implanted by the Lord, which is done without the person's awareness of it, he takes in truth and does good in freedom because he acts from affection. For whatever is done from affection, as has been stated, constitutes freedom; and the truth of faith joins itself in that case to good that stems from charity. Unless man has freedom in everything he thinks and wills, the Lord could not possibly implant within anybody the freedom to think what is true and to will what is good. For if a person is to be reformed he must think what is true as if from himself and do what is good as if from himself. And when he does so as if from himself he is in freedom. Otherwise no reformation or regeneration would ever be possible.