While an occasional passive-aggressive approach to life's problems isn't unusual, for some people manipulation and indirect communication are a way of life. Passive-aggressive people often go undetected in the office and in their social circles--at least initially--because they disguise their seething hostility with a pleasant demeanor.
Listen and relax when faced with a conflict and don't let your self-esteem be rattled. If you do happen to slip into a nonsensical disagreement, let the minor regression only serve to remind you of the giant steps in self-development you have taken. But, don't be smug about it, that would be unattractive.
As a psychiatrist I teach my patients to address passive aggressive behavior directly as the person may not be aware of the impact on you since they are short on empathy. Hopefully you won't have many passive aggressive people in your life, but if you do, clear communication is a form of empowerment.
Many people want to be more assertive in the workplace. Being assertive can help you voice your opinions to your coworkers, help you negotiate that promotion and pay raise, and also has a number of health benefits. Many people want to be more assertive but suffer from being too passive, abandoning their good ideas or not voicing their opinions to avoid conflict with others.