When you create a PAGE in WordPress, the PAGE title becomes a LINK on your NAVIGATION bar.
I like to keep them short for this very reason. ABOUT US, CONTACT US, SERVICES etc are best since the navigation bar is limited in size.
If you write a page title that says: We are circus clowns and would love to come to your town to perform, this is exactly how the link will show up on your navigation bar. If you do this, there will be no room left for any other links.