Time flows differently for us, Dean. Angels do not fear its passing, do not keep jealous tally of the seconds, minutes, hours, days. All time is... as it shall ever be. So if I fail to express the niceties you humans treasure whenever I "flutter off", do not think it signifies that you mean nothing to me.
My grace has touched your soul and bound our lives together. You are in my heart, my mind, my every breath. I could no more leave you than I could leave myself.
What need to say goodbye when we are never truly parted?