Don’t Reuse Passwords!

Password reuse is a serious problem because of the many password leaks that occur each year, even on large websites. When your password leaks, malicious individuals have an email address, username, and password combination they can try on other websites. If you use the same login information everywhere, a leak at one website could give people access to all your accounts. If someone gains access to your email account in this way, they could use password-reset links to access other websites, like your online banking or PayPal account.
To prevent password leaks from being so damaging, you need to use unique passwords on every website. These should also be strong passwords – long, unpredictable passwords that contain numbers and symbols.
Web geeks have hundreds of accounts to keep track of, while even the average person likely has tens of different passwords. Remembering such strong passwords is nearly impossible without resorting to some sort of trick. The ideal trick is a password manager that generates secure, random passwords for you and remembers them so you don’t have to.

http://www.howtogeek.com/141500/why-you-should-use-a-password-manager-and-how-to-get-started/