I'm not stupid
But I've gotten malware. I've not visited any sites that are not reputable, I don't willy nilly click on a pop-up, I block pop-up, clear my cache on exit, use 2 AV scanners, both with real time protection, and don't click on links in email or facebook, etc...
I still got a rather nasty infection with some malware. Luckily a trip over to malwarebytes, a nice cleaning in safe mode, and a few other tasks, got rid of it for me.
I tracked my infection back to a reputable news site and reported to them what happened. So, the point is that you can do everything right, and still get malware on your machine. In that case, you do need some good AV software, and a few tools to help you get rid of it.
