Yeah, password managers are the best solution to deal with the ever-increasing number of logins one has to remember.

Another alternative if you don't want to rely on any tool is to memorize an algorithm that you apply to the URL.

For instance, instead of memorizing a password for the website example.com, you could memorize an algorithm that turns the string "example.com" into a password. To illustrate, a very easy (and not secure) algorithm would be to add the number "1" after each letter, giving you "e1x1a1m1p1l1e1.1c1o1m1".

If you make your algorithm convoluted enough, it can give you decent security. But using a password manager is probably safer and much easier :-)