As we went over earlier, if a sufficiently advanced attacker wants to get into your stuff specifically, they will.
But we have looked at our threat model before and have determined we are probably not a person of interest to the NSA/Mossad/FSB, right? Right???
So according to our threat model, the most likely people to hack us will be random criminals who don't care who we are, they're just trying to get in. While it is an over simplification, "An ounce of prevention is worth a pound of cure". If you are able to harden yourself ahead of time and not be an easy target, you will be much less likely to get hit with a non-targeted attack, and in the possibility that you ever are targeted, you will be more likely to not get caught off guard.
These are some of the most common of the reasons you might get hacked.
You are already hacked!!
The most common way to get malware on your computer is to already have malware on your computer. Seriously, as I was first writing this section, I ran a scan on my shared family computer I am using and removed 5 separate PUPs and 1 piece of adware. Shared computers, whether family, work, or libraries, are hot places for malware to be sitting on, and if you log in to a owned computer, you might just lose your passwords to a keylogger. So let's make sure you are not owned already and then set ourselves up to be safe in the future.
How Can You Tell
Remember the term indicators of compromise (IOC) from before?. There are a ton that can be used, some approaches more technical than others. Common non-techical indicators include constant pop ups, home page redirection, search engine redirection, the classic pile of toolbars, and the computer being slow and the fans working way too hard. Technical indicators include extra processes running, network requests, and things saved in places they shouldn't be. Looking for these technical indicators is called "Threat Hunting". It deserves its own section, but we will briefly go over a few ways you can identify the bad things on your computer.