We all remember bullies from when we were kids; either personally or from being told over and over by teachers and administration about how bullying is bad. But what a lot of people don't realize is that bullies don't go away just because we grow up. Adult bullies exist, and they bully other adults. This bullying is almost always emotional abuse, unlike the stereotypical physical abuse of children dangling others by the ankle demanding each other's lunch money and shoving each other in lockers. And while as children we are taught to report other children emotionally abusing us, as adults, that disappears. Societally, bullies disappear in adulthood. But they don't. Whether the bullies are your coworkers or your boss or your landlord, or even your supposed friend; bullying can be just as much an adult problem as it is a child's. The result is a lot of adults being bullied without realizing they're being bullied because they assume it's normal.
As an adult, how do you avoid being bullied? First, stick to your principles. If bullies realize they can't bully you, most of the time they back down. Second, if someone is constantly criticizing you or demanding you do something personal a different way, get a second opinion. And a third. See if others have the same complaints. While it's possible whatever the complaint is indeed something you need to change, (for example being chronically 10 min late to work, that's on you) sometimes, whoever is making the complaints is just plain crazy. Say you're late once by 10 minutes and your boss yells at you for two hours about how you are a scum-of-the-earth worker and if you don't toe the line absolutely perfectly you'll be fired; it's not you. It's them. And that's not a good situation for you to be in. So stick to your principles. Don't change who you are to meet the ridiculous demands of someone else. If someone tries to push you around, stand firm. Stay yourself. Allow yourself to be human. If someone tries to make you less than human, don't stand for that. And if you find yourself being bullied by adults as an adult on a continuous basis (not just some asshole in the grocery store line who wants your spot. but like a boss or landlord) just tell them yes, and in the background do everything you can to remove yourself from that situation as quickly as possible.
Adult bullies gain power primarily by taking advantage of those with less experience than them. They view themselves as the elder, wiser of the two, and leverage that power to make the other miserable and overworked. They create new rules and punish you for not following the new rules they haven't even told you about yet. Most importantly, they make you feel like you're the problem. They make you feel like you are just not good enough, or not trying hard enough, and that's why you're failing. That's not true. They're setting impossible standards; not because you can't do what they want, but because by the time you do what they want, they want something completely different. It's a no-win situation.
It is important for adults, especially young adults, to realize that bullying is not just a problem in high school or elementary school. It may be different, more subtle forms of bullying that carry through into adulthood, but it is bullying, and we need to be aware of it because it is not okay. Even if the bullies end up being your parents (and I have known people for whom this is the case), it is still not okay. And it is 100% okay for you to leave a situation in which you are being bullied.
Never be afraid to ask for help and be on the lookout for toxic relationships, even as adults.