Doing the right thing is rarely ever coincides with doing the easiest thing. It's a good thing Windsor was with someone who had the strength to be with him every second of the way, doing everything you could, and ultimately the best thing. Knowing you did the "right" thing won't help to ease the pain, but try not to get too down on yourself.
Today I will have a moment of silence and smoke my last lucky strike (filter) in honor of Windsor.