"For it does many things through vicious desire, as though in forgetfulness
of itself. For it sees some things intrinsically excellent, in that more excellent nature which is God: and whereas it ought to remain steadfast that it may enjoy them, it is turned away from Him, by wishing to appropriate those things
to itself, and not to be like to Him by His gift , but to be what He is by its own, and it begins to move and slip gradually down into less and less, which it thinks to be more and more; for it is neither sufficient for itself, nor is
anything at all sufficient for it, if it withdraw from Him who is alone sufficient: and so through want and distress it becomes too intent upon its own actions and upon the unquiet delights which it obtains through them: and thus, by
the desire of acquiring knowledge from those things that are without, the nature of which it knows and loves, and which it feels can be lost unless held fast with anxious care, it loses its security, and thinks of itself so much the less,
in proportion as it feels the more secure that it cannot lose itself."
Notice the similarity to how "it" (the soul, in this passage) sins and how Melkior fell. The soul sins by wanting good things as its own rather than as God's gift. Melkior sinned by wanting to master the power of Creation, not have it as a gift from Iluvitar.
Is this post confusing, AGP?