Let it be known that I agree wholeheartedly with your sentiment punctuated in the last sentence of your post. I live (or at least, strive to) by that principle myself: live, not exist. Artificial prolonging at the expense of quality of life is a concept I find foolish. It matters not how long I live, but how I lived.
However, as with all things, balance and moderation is key. Contrary to what the aforementioned principle seemingly extols, I am not going to; for instance, start abusing drugs and die an addict, and claim it was worth it (not that I'd be able to, at that time) because I enjoyed it and thus lived fully. But I am not going to deprive myself from some pleasures in life that people seem to be so against, stupidly saying, "it's not good for your health!" just because I may die a year or two earlier than if I had forgone them. Like a cigarette (I'm not a smoker), or a really greasy burger from a street stall that I can feel clog my arteries.
Everyone is so afraid of mortality, of death, that they forget to really live. Everyone wants to live for a long time. Avoiding this food, or that activity, because it's "bad for health." When old age comes, I do not think lying in chronic, terminal illness in a hospice semi-conscious and all drugged up on morphine as living anymore. "I" am no longer alive. What makes me human is the component of my ego, and in such a state that component is largely gone. Then it really is just my body doing what it does to continue to exist. And I think it absolutely inhumane to keep a person alive in such a state.
Anyway, my rambling aside, goldens are inherently rather inquisitive. I imagine that to be one of the reasons as to why it got run over. As it is, though, it was a Darwinian-survival-of-the-fittest evolution scenario, no mistake about it. But it certainly could have done with a little bit of training -- and that, to me, is the moderation part of it all.