LizzyJB, I understand a lot of what you're saying.
I haven't had a friend pass away, but I have felt the guilt of feeling depressed and wishing my life would end while others are frantically fighting to survive every day. Some days I have wished that I could trade my life with someone who is dying, someone who deserves to live more and has more potential or more to offer the world.
Our circumstances are different, but I can relate somewhat to how you're feeling. Peace to you.