Once you get to know your dog well, you will be able to recognize his moods.
They will show in his body language, posture, facial and vocal expressions, and behaviour.
Just like humans, dogs experience moods of happiness, depression, frustration, contentment, anxiety, fear, anger and aggression.
It is up to each owner to learn to recognize their pet's moods in order to be able to ascertain how he is feeling, what he wants and what he needs, in order to provide him with an improve quality life.