Mysticism begins when the totally transcendent image of God starts to recede; and there's a deepening sense of God as immanent, present, here, now, within me. Augustine's line was "God is more intimate to me than I am to myself” or “more me than I am myself." St. Catherine of Genoa shouted it in the streets, "My deepest me is God!"
So you must overcome the gap to know—and then Someone Else is doing the knowing through you. God is no longer "out there." At this point, it's not like one has a new relationship with God; it's like one has a whole new God! “God himself is my counselor, and at night my innermost being instructs me,” says the Psalmist (16:7).
The mystics are those who are let in on this secret mystery of God's love affair with all souls, and recognize the simultaneous love affair with the individual soul—as if it were the only one God loves. It's absolutely our unique affair, and that sets the whole thing on a different and deeper ground than mere organized religion can ever achieve by itself.
Richard Rohr
Adapted from Following the Mystics
through the Narrow Gate (CD/DVD)