Among the animals, dog is the only one which loves human and obeys human. Even the dog cannot speak, but it can show by action to thank its master who takes care of it. Dog cannot live independently by itself. It cannot hurt prey to survive. They have to live together with human to live on their lives.
There are tens of thousands of dog categories. Their appearances and figures are different, some light color, some dark. Some has a shape like a rabbit and some as big as wolf. But, they have one thing in common. Those are their characters which loves human and obeys human. That is why human and dog can live together happily.
In western countries, many old women whose husband died and children went away, like to have dogs to accompany them. Dogs can wipe out their loneliness and give them sunshine life. Besides, dogs will never hurt them.
As far as human is connected, we do not know human heart which may hurt us in one way or another. Indeed human heart is mysterious and changeable, even we do not know our own heart which is also uncertain in certain circumstances.
We have to protect ourselves, not to be hurted by any person. The most simple way is to let other people to take a little advantage from us. A little loss to us should be no harm, but we can get rid of any trouble which may fall upon us in some occasion.