Death is just part of the cycle. Just the passing on to whatever comes next.
We make a big deal out of it, mostly because we are selfish, I would say. When someone passes over, we mourn them because WE want them to still be around. To fullfil a void in OUR life. In death there is no more pain, no stress, no more suffering - at least not in the sense that we know it now. Who knows what comes next? Something has to.
Everyone asks the question... why me? Why now? Why here? When you really think about those questions you realize there is more going on than our minds can fathom. Why me? Why now? Why here?
With all that being said, I'll be the first to admit I do get sad about relatives/friends/pets dying and if I had a S/O I'm sure the thought of her dying would terrify me. I think it's just human nature to take a selfish approach on death of loved ones. It's just natural to us. This is just interesting to me.