I'm sorry to hear about your dog, Mac. My parents backed over our cat once when I was little, but it was a quick death so we didn't face the trial of trying to save it. I can't imagine what you are going through.
What gave me mixed feelings is reading history books. It's all written to be light reading - one about the history of formal botany, one about humans and food, and one about Hawaii - but some of the stuff recounted is pretty heavy. It makes me sad to know the particulars of the darker parts of human history, but it makes me happy to be reminded exactly how well I have it. My life is so much easier for being born in the current era and in my country, and I am thrilled with the relative comfort and long lifespan I have access to.