It’s really important to not use the same password on more than one site. With hundreds of passwords to keep track of, you really need to use a password manager. This is an application that looks after your passwords for you in a highly secure database which is encrypted and secured with a single really good password (that you do need to remember). Such a tool enables you to have a different, really complex password for each site and system that you access. A good password manager will enter the details for you when needed to access a site or system. This has the added benefit of protecting you from phishing, as it will only offer you the password for the correct website.
There are many password managers out there, but I can highly recommend RoboForm, as it’s the one that I trust my own passwords to, and I’ve been using it for years. There’s a free version that you can use, but in my view it’s well worth paying for the RoboForm Everywhere version. For less than £15 a year, it will sync your passwords safely and securely across all devices that you use, including mobile phones, tablets, laptops, etc.
You will find RoboForm here.