"God [is] Spirit, and those who worship Him must worship in spirit and truth." John 4:24

"Spirit the God" is the original and "is" is an addition by the various translators so Spirit would be God's absolute nature, it is not an attribute like God is Light, or power majesty and glory etc. Everyone has a spirit so we all have God's absolute nature, so "God is All in All."

Man is not aware of his state as spirit, he may know it intellectually but cannot experience it. Man as a tripartrite being is like muddy water that is constantly stirred by man's thoughts, so it can never settle down.
If man could only shut up, and let go of our self importance and the wisdom of his own thoughts the mud would soon settle down and we would see clearly.

The chief obstacle from which all others are derived, is undoubtably the fact that man in his waking state does not see he is asleep and has forgotten his real SELF/GOD.