You may have a password for your computer logon session, however thinking of a suitable password is always a burden, for example people always use their birth date or last name + birth date as their password, for example "beng77" or "42kamal". Well this is not very secure as people can always try this out and attempts to use your password.
Secondly, you may change your password frequently or the server operator can set an expiry date that controls the age of logon passwords. This idea is not so good, as it force the users to think of a new password every time the server password expires.
The idea is to use a pass-phrase or a continuous meaningful string of words. For example like "Iliketovisitthecameronhighlands" or "P@s5w0rds" as the password which is unlikely to be easily known or to be crack. In addition, spaces can be treated as a character other than punctuations, lower-upper case and symbols ($#@>+<,) are usable as a character.
Think about it...