Project the calmness you'd like to see in your relationship. While there's not much you can do to keep your sister from flying off the handle at the slightest mention that she should reconsider her decision to let her 10-year-old watch "The Exorcist," you can resist the urge to reflect her anger, sadness or other negative emotions. If your sister begins to rant or cries when she learns that you were invited to your uncle's birthday party and she wasn't -- simply listen and give calm, compassionate responses.

Resist the urge to ruminate on past arguments or wrongdoing. Rather than gaining insight, you're likely to feel worse, says psychologist Guy Winch in a July 2013 article in "Psychology Today." Rather, catch yourself when you are dwelling on how your sister hogged all the attention at your last gathering and distract yourself instead with an activity you enjoy.

Sibling rivalry between sisters often appears in the form of passive-aggression, says psychologist Jeanne Safer in a March 2012 article in "The Wall Street Journal." If you find yourself seething because your sister told you that you look much better in your bathing suit "than you did last year," let it roll off your back. Chances are, she is still remembering the time your mother told her she would do well to adopt your healthy eating habit.

Apologize when you are in the wrong. Doing so can help you to repair the relationship. When you apologize, says Winch, do so with empathy, so your apology comes across as sincere. When your sister feels that you are authentically trying to improve your relationship, she is more likely to be forgiving of your missteps.

Look at situations from your sister's point of view, advises Winch. Perhaps mother always told her that she was "the smart one" but now she is envious of your career, your wardrobe and your hair stylist. If she becomes upset when your parents keep crowing about your success to your extended family during the Christmas holidays, consider that she may be feeling insecure and seek to build up her esteem.

Focus on the positive aspects of your relationship. While it is true that she might be unwilling to babysit your kids or become irate at the mere hint that she might have a dysfunctional marriage, you can improve your relationship by emphasizing the aspects you like. Perhaps she knows every family story by heart and can tell you how your great-grandmother and great-grandfather met. Or, maybe she never fails to bring you a pot of her amazing chicken soup when you are sick. Whatever it is, focus on the positive when you are tempted to hang up the phone during an emotional conversation.