Unless anyone has had a dog they will not fully understand how you feel.
I too have suffered the loss of close friends and relatives but somehow, because the dog is with you all the time, hero-worships you and is totally dependant and trusting of you, it seems so much worse at the time!
I have an eleven year old and my real regret is that we had her spayed before she had any pups because I think that, whilst she is irreplaceable, if you have two dogs, somehow, you have some comfort if/when something happens.
It is too late for us because our little girl would never cope with another dog in the house after being the centre of attention all her life.
Stupid aren't we?