Our call demands union with God, because if it is God who calls us, union in Him is the way to know Him whom we are proclaiming or else we are proclaiming someone we do not know. Union with God means detachment from everything that prevents it otherwise.
Saint John of the Cross once said, “The soul that is attached to anything however much good there may be in it, will not arrive at the liberty of divine union. For whether it be a strong wire rope or a slender and delicate thread that holds the bird, it matters not, if it really holds it fast; for, until the cord be broken the bird cannot fly.”