Have conviction in your beliefs. Stand up for yourself and your values.
But also have an open mind. Realize that situations are often way more complex than they might seem. You don’t always have all of the data, the right perspective, or the necessary background/experience. All of this adds up to the fact that you should be open to hearing the other side, learning, and change. Ultimately, it’s the bigger person who can acknowledge s/he was wrong and fix it.
This is VERY important in both your personal and your professional life. For your social life, it makes you a more accepting person and more fun to be around. If you are an executive in a company, this willingness to change and update based on new information is critical to long-term success.