Vizier that's why you use a system, like a static base password that is modified by a particular and easy to remember system. Such as the last three letters of the site the 2nd letter being uppercase as the middle portion of the alphabetic and numeric portion that is the same to all sites. Obviously don't use that system =) But you should see how easy it can be to remember complex password that are different for every individual location.
Password managers are like handing hackers you entire system on a silver platter, it has to be kept in your head. If you can't do this then the primary security vulnerability is yourself.