Never Use the Same Password for Important Accounts
I would say the most important account is your email, you definitely want the password to be unique at all costs. Once your email password gets stolen, all your accounts using that email will fall like dominoes. How? By using password resets!
Here’s an example. There are some sites that don’t take security seriously or maybe whoever is building them is incompetent, so if you use the same password on those sites and they get hacked now they have a password that they can try on your email and if it was the same password then you’re out of luck.
Sites should always “hash” your passwords before storing them in their database, that means that they should go through a math function that scrambles the letters into other letters and symbols. In the event of the hack, all the hackers would have is jibberish, which would be hard to reverse unless your password is something simple like “password1234”.