Repeat after me:
I cannot control anyone's behavior other than my own.
I will not give negative people space in my head. They have no power over me unless I give it to them.
I don't care if people like me as long as I like me.

Say it, Practice it, Believe it. Trust me - when you stop giving the negative things so much of your energy, you will feel better. Some days are much harder than others but you can get through it. :)