As there are many systems, and we may choose similar/same passwords to most of them.
Do you know whether, your user credentials have been in any breach?
There is a Web Service created by Troy hunt.
Note: This is an educational site.
Go to the URL and enter your email address.
Have I been pwned? allows you to search across multiple data breaches to see if your email addresses has been compromised., often with the same passwords which then put the victims at further risk of their other accounts being compromised.
Lesson: Never Choose same passwords for multiple accounts.
Noting the passwords on Online Docs is also not secure.
Possible way: Instead of Passwords, Note the Hints.
Hint Like: Smith
Smith is well known word, But it is hard to know the password - whether it would be "Cricketer or Name of Country Smith Played or Which Smith or a Restaurant Name"
There are few software services which can generate secure passwords.
Remember: These are also less secure.
Read about -
The Best well known password secure storage is Your Brain.