When a dog looks sad to you (has his head down, not making eye contact, etc) - he's actually content and happy.
That's not true, head down is a bad sign for a dogs happiness and confidence. They should not always be avoiding all eye contact, I'm sure some may say staring you down with an aggressive stance is a warning.
Just like tail wagging is not always a sign a dog is happy or friendly. A low wag/ dropped back ears usually means a friendly not aggressive dog. A straight up wagging tail and ears forward usually means the dog is in an aggressive state. A sad dog is a lot more recognizable than a friendly happy one to most people.
Please make sure those tie downs don't fail.