Everyone wants to be liked regardless of who is in the room, but most people have the sense to hide that info. As a child I was extremely vulnerable and sensitive, and to make things worse I would hand over my peers the tools to torment me. In my efforts to win a crowd I would turn them against me by being an easy target.
In my home there wasn't much positive social interaction, so I had to learn how to act on the fly. I was really bad at making friends. Guys couldn't tease me, I get so upset because I didn't realize that negitive words didn't mean they had a personal hatred of me. I would carry grudges because I felt personally attacked. Eventually the people that figured out my anger towards them would really begin to hate me.
Once you have been hated for so long and made yourself an enemy of everybody you tend to start to understand how to act under the curcumstances. I'm skipping a lot of personal history here, but I've learned a lot about people.
You will always give someone a reason to dislike you, even if it's not a good reason or your fault. So don't be caught off guard.
You don't have to care about every single person on the planet, just people that matter to you. Which translates to you shouldn't be upset if some no-name from floor 6 called you a *****.
Sometimes people will be senselessly (and infuriatingly) cruel to you, but it's not because they hate you. You could be a scapegoat for whatever is happening in their personal life.
If someone has made a personal vendetta against you the best way to deal with it is to treat their behavior as a minor thing. Nothing is more infuriating then wasted time, effort, and breath towards someone who couldn't give two *****.
Save your insecurities for people that deserve to see them. If someone is majorly bashing you on something that is close to your heart and you're not friends or emotionally involved with them, simply do not let them in. They don't deserve your honest response, save it for people that do.
And lastly, and I can't stress this enough, really don't care about what other people think. So many people claim not to care, but really learn it.