Perfect

 None more true, none more faithful, none more loving.

The space that a dog occupies in your life, when that dog is a true member of your family, is a space that you could not have known existed before that dog came along.   

The space that's left behind when they're gone is not like any other.  It's an emptiness that can't be satisfied, can't be filled, can't be repaired.   When we lost our lab, my wife pointed out to me that, although there were plenty of times where we may have lost our patience with the dog's behavior, became frustrated or angry with her, she was utterly incapable of ever feeling the same for us.   Never was there a moment where she was angry with us, upset with us, impatient with us, nor betrayed us in any way.   This is common, i think, to all dogs, and this is what makes them perfect, in all ways.