Have you noticed that Swedes keep calm in public and that they hardly ever seem to argue with each other? Guess what! They do. But in their own subliminal way, which could be hard to read if you are only used to meet people from more extrovert and louder speaking cultures like the Spanish or Italian for example. Swedes generally speak with a lower voice and express themselves in subtle ways.
Don't be fooled by the melody of the Swedish language. Just because they use very pleasant sounds, it doesn't mean that they are all happy all the time.
So be aware next time you're in Sweden for vacation, the lovely couple sitting next to you in a cafe might actually have a serious argument.