I used to do this. It fell apart fast. Some websites require special characters and numbers and upper and lower case letters. Others actually prohibit certain s

I used to do this. It fell apart fast. Some websites require special characters and numbers and upper and lower case letters. Others actually prohibit certain special characters (weak SQL injection "prevention"). Some limit the length to 8 or 16 characters, others don't. Then a random breach happens, and the website will force you to choose a new password. I couldn't remember which variant of my rule I used at a particular website. This is aside from how easy my rule was to reverse engineer (which was made really clear to me once when I saw a couple of my PWs on haveibeenpwned