They both have a "little state" complex. Slovaks are quiet (and well.. not many people know about them) because of it, but Czechs are pretty much loud and make fun of everyone who live in country...
Czech Rep. and Slovakia are countries of Slavic origin. In 10th century when Hungarian tribes settled on their current territory, the territory of Czechs and Slovaks was known as the Great Moravian...
People have different emotions for different people because many people are different then what you think you'll never know the person until you actually spend time with them and never hang around...