In most environments it does not matter how good your firewall is configured. It does not matter if all of your programs and apps are bug free. If you have as easily guessed password you might as well not have a password at all. There are two groups of passwords people use today. The most common are ones you to access other computer system such as a web site or a router. The other kind of passwords are on your own computer to keep unauthorized users out such as to log into windows or linux or to allow people to access shared folders. Sadly most Windows home users turn off the log in. They find it too much of a hassle. While the odds are low, someone could steal break in to your house and steal your computer and then have access to everything on your hard drive. The odds are much higher if you have a laptop and take it out in public. Even once. One last thing. Your wifi password. Not the one to log into the router itself but the one you use to connect to the actual network. It's real important it is a good one since it allows people access to your entire network.
First, don't use easily guessed passwords. Some famous passwords
are sex,root and god. These are among the first ones a hacker will try.
Don't make the password something obvious like your userid. Don't
use password as your password. And don't make your password blank.
When selecting a password do not use a word that is in the dictionary.
There are programs that can take a list of known words and try them one
at a time until entry is gained. Use a mix of numbers and letters and symbols.
Maybe try misspelling some words like:
cookiebox => kookieb0x
spaceship => sp8ceshep
The longer it is the harder it will be to break. It should be 8 characters or longer. There are hacker tools that can try random groups of characters. But this takes time. The more characters in the word the more combinations there are and thus the longer it take to get to it. Computers are very powerful today and are only getting faster every year.
For extra security change your passwords every month. You should not use the same password for multiple systems either. Once someone figures out your password one one web site they would gain access to everything you have. You can limit the damage they could do or the amount of information they could steal by not using the same exact password for your windows login, your email account,your playstation 4, your amazon account,etc. As an absolute minimum don't use the same password you use on your really important things like your checking account. Another really good idea is to use a password manager. This was you can have different passwords everywhere but don't have to worry about remebering them. You only need to remember the one to the password manager.
Watch out for passwords in hardware such as a wireless router or a cable modem. Be sure to change it from the factory default. It's not very secure if your password is in the manual that it came with.
You may dislike using passwords that are a little hard to remember, but security is no longer a laughing matter. When someone breaks into your computer and/or network the cost to repair the damage can be pretty big in time and money.