Be positive! Everyone likes to work with an upbeat person.

But make sure you do not exagerate. If you move from the states to the old continent, calm down! If you move to one of the ex-socialistic countries calm down even further. It's OK to be positive, just don't make too much fuss about it. Even if you are the boss, calm down. We've acquired alergy to the prophets of bright future, your boasts about the company's profit and future will not go down well.