That's why it's crucial to install and use a password manager. These programs are designed to store all kinds of critical information: passwords, credit cards, Social Security numbers, software registrations, and so on. Once you've entered your data, you need to remember only one password: the one that unlocks the program.
I use my password manager almost daily. When I buy something online, I don't have to run upstairs to find my wallet--I just copy and paste the number out of the password manager. Likewise, if I can't remember the password I chose for, say, a photo-sharing site I signed up for three months ago, I don't have to go through the "forgot password" process--I just fire up the program.
I won't say which password manager I use, because it's years out of date and I'm in the process of migrating to a new one. I will say there are countless commercial programs to choose from and a handful of freebies. In the latter category, , offering robust features like password generation and auto-fill (it automatically inserts passwords where necessary). You can get the 1.14 version at the above link or .
The most critical feature for me is synchronization support for whatever smartphone I happen to be using (an , currently), so I have my passwords and other data at my fingertips wherever I ago--but still protected and encrypted just in case the phone goes missing. Two programs that fit the bill are and , both simple but effective password managers.
What's your password manager of choice? Or are you still trying to keep them all straight in your head?