Why not use a Password Manager?
Pros and Cons exist when using a Password Manager, but it sounds like the pros might outweigh the cons in your situation.
Pros: Many of them will generate complex passwords for you, encrypt them with a cryptographic key generated from a master password, and save the ciphertext. Many are companies and if security issues exist it could cost them their reputation (and their jobs).
Cons: Some password managers are internet based and could have availability issues. Trusting them to do what they say they do. How do you know the next version of a password manager won't compromise the security of your passwords?
Some password manager examples are.
- many others.
Shop around and see which one best suits your needs.
edit: If you are forgetting passwords to your password manager there is no hope for you. There are certain things in life that you must memorize, and a password is one of them. Password managers can help but they can't do everything. If there was a solution that allowed you to not remember a password ever then password managers would do it.
One thing you could do is risky. Choose a weak password for your password manager and use 2-factor authentication on password manager, which stores your secure password.
This is super risky though. If an attacker is able to guess your 2factor key, you would be in a lot of trouble (since they will definitely guess your weak password). They also might be able to revoke access to your second factor or use social engineer techniques on help-desk employees at a password manager company to compromise you. It should be noted that because of this, if you choose to use this solution, you had better use 2factor on all sites you can, along with the secure password.
This is super super super risky. I don't know why anyone would use a weak password to their password manager, but it is a solution to your problem.