The reason password protection is used in the first place is to safeguard information that is sensitive. Whether that information is proprietary or personal, its obvious value is demonstrated by the fact that someone believed it was important enough to put a password on it in the first place. When used properly, passwords form one of the most impenetrable shields for systems and information that exists.
Strong passwords are impossible to guess and easy to remember.
With a little forethought, they're also easy to make. Go to Building a Better Password for some help getting started. Weak passwords are almost worse than no passwords at all, because they afford the illusion of security where there is none.