Yeah, it's hard even when your browser remembers passwords for you. I have a list of what passwords go with which website but it's easy to forget making changes to it when you do so online. What is your system for doing this? Read more with a link to their guide for internet security @ http://www.foxnews.com/tech/2014/08/25/problem-with-passwords/
http://www.roboform.com/ is an excellent password manager. However I don't use it myself, but I know a few who do.
I keep my passwords written down and in a paper file cabinet. The sites I visit weekly and have complicated passwords I keep the passwords on a piece of paper at my PC desk. But I use a code when I write them down by adding several digits before and after the passwords. Thus I'm the only one who can correctly copy the password. For simple websites I let Windows remember my passwords. . I get aggravated by sites that ask you to choose a User Name and a Password. Then when you go back to log in they ask you for your ID and Password. Then you find out the ID is your e-mail address.