How many passwords does one person need....

I get that you need a password to log into stuff to make sure that it's really you. I get that you need a pasword to log into case sensitive stuff. I get it, really I do. What I don't get is why I have 50 (maybe more) different passwords, some in various forms of others, and I can't remember them all. So guess what I do?? I write them down. Oh, yes, I do! How else am I supposed to remember them? I have passwords for email, password for school stuff, for blogging, for each and every site that I order things at (make your life easier, create an account--easier my behind!) Anyway, that is my rant for the day....I'm having a complete memory lapse and it's really irritating me.