At this point, it seems as though there's a new data breach every week where users usernames, passwords and other personal information has been exposed to hackers. Keeping track of them all can be quite the undertaking.
Passprotect is a Chrome extension that uses data from the site Have I Been Pwned to let you know if a password you're using has been found in any data breaches. If it has, then it's time to change it.
To get it, click on this link to the Google Chrome store and then click "Add to Chrome" from the top-right side of the page that pops up.
A good way to avoid this problem in the first place is to use a password manager such as 1Password to create and store secure passwords. Passwords are randomly generated a hard to crack, making them ultimately a bit safer than anything you probably can come up with on your own. 1Password already compares its passwords with the Pwned database.
And in general, it's a good idea to check yourself out on Have I Been Pwned every now and then. The site just asks you to enter your email address and then will let you know what data breaches that address was involved in and what information hackers took. In my case I was involved in seven, most of which I knew about but a few I did not. Like most things, you're better off safe than sorry.