Recently i got a new job, and my boss influences me badly. I  was doing well, but his attitude gets to me.  Right now this place is the best shot i got and he has a good chance to leave the place to me and move abroad. So i need to suck it up and take it for a while. Meanwhile i'm trying to find ways to cope with him so i wont fall apart again like i did twice last month.

He's one of those people : you cannot trust what he says and you cannot give him 10 bucks. He'll never give it back. He frequently mocks my chronic back pain, doesnt care about buying supplies or cleaning, (we both should be doing that, not just me), slightly disrespects me while not stepping on any obvious borders, so i can't say anything without sounding like a total butthurt bitch. He's dating this girl. Paying her bills, rent and credit cards, buying expensive gifts and stuff. She gets super annoyed by him. He spends 100% his time trying to satisfy her and she ends up getting more and more annoyed,then they eventually fight.  he's such a bad person i honestly think he deserves this kind of fucked up relationship. He has confidence, over the roof. I'm pretty sure all of you ran into these at least once in your life. 

TL;DR: Thanks to my bpd, i realized after two months with a douchebag, my confidence is draining fast. His bad energy is really getting to me. How do you cope with a situation like this? How do you cope with very negative people?