Whether you're asking your boss for a raise, or you're talking to your partner about where to spend the holidays this year, effective negotiating skills are important. Limited self-awareness about when you're being too pushy and when you're not speaking up enough can wreak havoc on your relationships.
Realize that there's a difference between bitterness and anger. As Maya Angelou so eloquently put it, "Bitterness is like cancer. It eats upon the host. It doesn't do anything to the object of its displeasure." Contrast this with anger -- it's okay to be angry, as long as you channel that energy productively.
The workplace often brings out conflict. When you are passionate about your work and good at your job, you're not always going to agree with everyone. In fact, conflicting viewpoints are part of what makes a workplace creative and productive. But conflict doesn't have to ruin your day or damage your relationship with your colleagues.
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.