You will be finding negativity every step of your career. If his negative character is influencing your work life balance then he is successful in doing that and he has successfully influenced you to become like him. Whenever I see such kind of behaviour and people I keep reminding myself that I surely don't want to be that person and treat him nicely and not as he treats me. If you keep treating him nicely, no matter how many times he shows rudeness he will be compelled to bow down ultimately. In summary, Don't let other to change your true character. Just be who you are and let fate decide because it never goes wrong.