My computer was badly hacked a couple of years ago. I changed all my passwords, and no two are alike now. Otherwise finding out just one could lead hackers to all of them.
They say don't use the same password for everything, and I ignored it because I keep forgetting them. But I built one which is watertight and I won't forget, by using the same one but including a code that refers to the site I'm entering. A very simplified one would be birthdayam for amazon and birthdayne for Netflix, but it's nowhere NEAR as easy as that! (upper & lower case, some complicated code from the website name, an extra word, strategically placed symbols etc, a very obscure foreign name, a number - but not in that order. I always get them right, they're all different, though it does take some time to input them, and just a few I have to remember to leave something out as this one has a cap on the length and that one doesn't allow symbols.