Memorizing your passwords is the best way to keep them.
If you cannot do that then you need a password manager to help you keep them safe and secure.
You can use LastPass (https://lastpass.com/f?38363352) especially for your web applications or portals.
LastPass is an online password manager and form filler that makes web browsing easier and more secure.
You can also use Keepass (http://keepass.info/), it’s a free open source password manager, which helps you to manage your passwords in a secure way by creating an encrypted database of your passwords on your local computer.