Someone being able to get a hold of or crack your passwords can wreak havok on your life in many ways. If it's your email, then many other sites will use that to do password resets (the "forgot my password" button) unless you are also using 2 factor autherntication. Even worse, many people also reuse passwords for many things, so often when someone gets one of your passwords, the first thing they will do is try it out on other services. A great tool is Have I Been Pwned - this will allow you to see if any of your passwords are already out there. Bear in mind though that they may take a while to show up there.
The next thing is that you really should be using is a password manager. There are many of these out there, but here are some I like:
Finally, using two factor authentication, or 2FA as it is sometimes known, for any service that offers it, can really save your bacon! The simplest free solution is to use an authenticator app. Again, here are some options:
I personally prefer to use a security key such as a Yubikey. You DO need to purchase these, but I find them to be a simpler, and more secure way to do this. I also like the paradigm of using a phsical 'key' to unlock stuff.
Hopefully this has given you some useful ideas on where to get started, but as always, there a million useful articles out there to help you out and almost as many ways to go about this. I just wanted to shout out some of my prefered solutions, Hope this helps!