Jesus said to the crowds,
“And this is the will of the one who sent me,
that I should not lose anything of what he gave me,
but that I should raise it on the last day.
For this is the will of my Father,
that everyone who sees the Son and believes in him
may have eternal life,
and I shall raise him on the last day.”
~ John 6:39-40
Matter is indestructible. It merely changes is shape and form. Break down molecules of water into its component parts, you will always get twice as much hydrogen atoms than oxygen atoms. Breakdown salt into is components, you will always get equal number of sodium atoms and chlorine atoms. No more, no less. And yet over all that matter and tripping all over those atoms, there hovers and skips a consciousness and an awareness that animates all matter. We experience that as the spirit.
Spirit seems to need matter to exist. It is through our bodies that we are aware of the world around us. And yet, when we sleep and when the body is almost non-functional we are still conscious and aware of ourselves. There lies our dreams, our unconscious and our subconscious. This awareness and consciousness seeks for its source, its cause and its ultimate end. I do not fully understand all of this but it is what I know Christ was talking of when He talks of coming from the Father and going back to Him.