When it comes to passwords we want sequences that are easy to remember but hard to figure out. As Baekdal.com writes, this rock and hard place is not necessary:
Security companies and IT people constantly tells us that we should use complex and difficult passwords. This is bad advice, because you can actually make usable, easy to remember and highly secure passwords. In fact, usable passwords are often far better than complex ones.
In one of the best articles I’ve seen on password security, Baekdal.com describes an easy way to develop secure passwords…using passphrases instead.