So even if I come up with memorable passwords like "correct horse battery staple," I don't think I'll be able to remember a unique password for the dozens upon dozens of sites I visit. Thus, the alternative is to either repeat your passwords across multiple sites (not recommended AFAIK, since if one site stores passwords insecurely, all your other accounts with that password would be vulnerable), or to have some way of saving your passwords so that you don't have to remember them all.
I've been thinking of using LastPass or 1Password and other similar services to safely store and generate unique passwords. But if I'm going to be using those password managers, I am of course going to have to have them autofill my passwords for me. If that's the case, how am I going to prevent my passwords/accounts from being stolen if my computer is stolen?