Getting to know a new dog can sometimes be a challenge. As much as we try not to, we end up with preconceived ideas about how a new friend is going to act based on our experience of other dogs we've lived with.
We wouldn't expect a new friend to treat us based upon their experiences with old friends; we expect to start with a clean slate. We want to be judged as ourselves; as an individual. And then some people turn around and expect a new dog to act like their old dog.
Expectations are an inevitable consequence of wanting to share our lives with new friend; we want to share more of those experiences with another species... That's quite an amazing thing in itself, really. We can sometimes miss the obvious - even miss the extraordinary - because we're relying on our old experiences to guide us through.
Experience is great; but remember that it's a foundation upon which to build new knowledge. You should never look at the experience you have and think "that's it!"
As Sir Francis Bacon said, "If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts he shall end in certainties."