You may need help with remembering your passwords. If you have to write them down, only put enough to jog your memory, never the whole thing. Follow National Cyber Security Centre advice by keeping any passwords that you write down safe, out of sight and away from your device.
If your device is secure, save your passwords to a web browser. You may need to select this option in the browser’s settings if it doesn’t automatically give you a choice.
You can also use a password manager.