When he, the Spirit of truth, comes, he will guide you into all truth . . . He will bring glory to me by taking from what is mine and making it known to you.
(John 16:13-14, NIV)
Union with God is not a feeling. It is not merely an emotion.
Fellowship with God is not brought about by human imagination or understanding.
Rather, as we trust God, He gives us His Spirit to live within us. His Spirit leads us to God and lifts us to Him. He nurtures a desire to love God, to worship Him, to turn our minds and lives to Him more and more.
As we respond to God, a union grows that is beautiful and indefinable. It is peaceful, reverent, loving, personal, and very simple.