One wonders how many of us attempt to learn their language. They understand and react to body language far better than we do. A dog understands that closed eyes and a head turned away means, "go away, I don't want to interact with you right now." Waving arms to us means "don't jump up and dirty my clothes." But to your dog it means "come and play." To get the "go away" message across we should put our hands under our armpits and avert our heads. They would so appreciate our efforts to learn their language. The fact that we don't doesn't lessen their love for us.
Of course there are many different species that become part of our lives. The cats, birds, horses, hamsters and even rats that share our lives are all sorely missed when they leave us. We miss those big brown eyes, that gentle purr and the merry chirping that brightened our lives. Unfortunately the life expectancy of most of our pets, except of course, parrots, is much less than ours so we may well suffer this loss many times and, for the animal lover, it is something we never get used to.