Just use a password manager! I use KeePass 2 and its honestly made logging into things so much easier. It's a long process to change ALL of your passwords, but it's worth it. Being able to sign in anywhere with a few clicks without having to remember your 20 character 127 bit alphanumeric password, which consists of lowercase letters, uppercase letters, numerals, and special characters. No one is going to guess that. No one is going to hack that. If there's a breach or on the off chance someone does guess or hack your password, that's the only account that's compromised. Depending on the account all of your other accounts are still completely safe. Then you don't have to think of a new a password, because you can just generate a new super complex one and save it, then paste that into the new password field in your account recovery. If you are going to be selling and worrying about OPSEC, I think it would be stupid not to invest in a password manager, at least for your more illicit online activities. If you don't and you use a stupid password like "asshole209", then you are putting not only yourself, but ALL of your customers, anyone you've contacted, and any information saved on that and related accounts (address, email, other sensitive data).
tldr: Use a password manager, at least for illicit activities. It's super easy to setup and use, and you can keep your accounts secure from normal password hacks, and leaks. Things like "asshole209" are not good passwords. I recommend KeePass: Professional Edition. Please don't put yourself or your customers at risk.
tails users please follow this https://www.reddit.com/r/DarkNetMarketsNoobs/wiki/bible/buyer/dnm/usingkeepassx