We seek this Oneness because the call for it was placed in our souls by God. Jesus even tells us that Heaven is the awareness of perfect Oneness, “nothing outside this oneness, and nothing else within.” (T-18.VI.1:6) Because we are learning through the A Course in Miracles, we find this Oneness first through our relationships, in particular the chosen learning partner(s) who offer us unlimited ways to learn of love. These are the ones for whom we are ready, the ones to whom we remain connected lifelong. And these relationships generally are few. (M-3.5:3) The Course says that we may not even recognize the perfect matching that has occurred in these relationships. But the perfect lesson, the lesson of genuine love of ourselves, others, and God, is there for us if we do not break off the relationship prematurely. This then is the special relationship that can become holy, indeed that is meant to become holy.
And forgiveness points the way.
MIRACLES EACH DAY 
Fortunately, if we are Christian (accepted Jesus Christ as our savior), at the point of salvation we take on a new nature (spiritual) that is permanently set apart (the meaning of Holy) from all unsaved humanity. Unfortunately, we retain our sin nature, therefore, we will continue to sin (as noted by the Apostle Paul – Romans 7:13-25). While our spiritual nature remains Holy, our sin nature continues to entice us to return to our old ways. Using 1 John 1:9 is our only option to return back to where God wants us. While we will always remain children of God, the unsaved remain children of Satan until they accept Jesus Christ as their savior. To be Holy is a permanent status for the Saved.