Union with God is loving God with all you've got, the giving of yourself to God. It is an unspoken, simple but profound, most intimate relationship with the Lord. You open yourself 100% to him and he communes with you freely. It is imitating how God the Father and God the Son are in each other. Above all, it is what God desires from us. Union is achieved by submitting yourself completely to God. When that happens, he takes over and accomplishes all that's impossible for you to accomplish. It's letting God be God. We struggle hard only because we have not let God reign over our private little kingdom. Union is for you and me, for everyone! Why do you not consider it? Is it because you don't think you are good enough? Then let God make you good enough! Is it because you don't think he can make it happen to you? Then you don't believe that nothing is impossible with God! You don't need to be a mystic or saint first; it is in union that they become mystics and saints. Short of union, you remain struggling through your life, which strictly speaking, is rebelling against God.