Password managers can help you to manage your passwords. They allow you to put all your passwords in a single database locked with one master key or a key file. The database itself is encrypted using various encryption algorithms. You only have to remember one single master password, or select the key file to unlock the whole database.
We recommend Keypass (Windows) / Macpass (MacOS).

But do not forget: keep your master password secret and in a safe location (e.g. in your head)!