Growing up, I hated upsetting people. I always let people walk all over me even when I didn't deserve it.
You have to pick and choose your battles. Knowing when to stand up for yourself and when to just walk away as well. I always just walk away not only because I hate upsetting people, but because I get scattered brained and don't know what to say because I can never process most of the time how people could be so rude. There are people out there who can turn bad situations into good leading you to believe that you're in the wrong and they aren't, even when you did nothing wrong.
Then you have those people who you never talk to but for some reason, they feel they need to comment on everything you do, talk a lot of crap about you behind your back, and just tear you down every second they get. Even when they don't know anything about you or maybe even when you're super sweet to them hoping they'll do the same in return.
Then I realized something. People are rude to you to make themselves feel better. Maybe they're jealous or insecure or even feel like they have a little competition. Whatever the reason may be, if you are getting tore down by the same person/people, you have to start sticking up for yourself.
If you're one of those people that don't care what people say or think about you and feel like it's best to walk away, then that's okay. But when that point comes to when you just can't handle it anymore (which you'll reach that point eventually), pick yourself up and know that what they're doing is not okay. You have a voice just like them. And if you're afraid of what the outcome may be after you fight back with your words, just know that they have nothing to lose. They already don't like you for some reason. I'm not saying stoop down to their level and tear the down, you can fight back in a classy way.
Something that helps me is I'll practice certain situations that have happened to me in the past or maybe a made up situation that actually hasn't happened in the shower or driving. Pretty much just anywhere I'm by myself. Looking myself in the mirror always helps me the most just because I can see how "intimidating" my face looks (LOL). Super embarrassing but I know I'm not the only one who does this!
Like I said, you have to pick and choose your battles. But just know that you are so much worth than anyone could ever label you. Demand respect and most of all, RESPECT YOURSELF. No one knows your story and has no right to tear you down.
P.S. How you make others feel about themselves says a lot about who you are. Be the person that people can come to or just thinks nothing but the world about you.