Things have been tense in the office for a while now, but last Friday, they came to a head. Jane, the talented and outrageous marketing director for a global apparel company, stirred up trouble—again. One of her staff made the mistake of pushing an idea in a meeting that was different from Jane’s, and instead of hearing him out, Jane publicly berated his idea. After the meeting, doors slammed, whispering and gossip ensued, and her direct report left the office early and in tears. Jane’s behavior had finally reached the point where her boss couldn’t look the other way. Jane is “that one” who for years has been allowed to behave badly because she delivers so smashingly well.

Now Human Resources needs to figure out how to help this highly educated, numbers-driven, and painfully difficult person soften her approach. When HR asked about her outburst, Jane nonchalantly and confidently stated, “You know, it’s just who I am and how I’ve always been.” With one staff member already out on a stress claim, Jane is headed for coaching, not realizing how close she is to being fired and ruining her career.

“It’s just who I am” is one of those classic excuses people use to explain bad behavior in and out of the workplace. We may not be as harsh as Jane, but we’ve all had moments when we are our own worst enemies. For Jane, these moments have added up to the point where—like a leak in a tire—she is slowly deflating all the progress she’s made over the course of her career.

How can this excuse ruin a career? In short, it’s an excuse for bad behavior that’s both avoidable and can cause a lot of damage in the workplace. Jane is describing what she thinks is her personality. Personality—or who you are—is the collection of your motivations, needs, and preferences (like preferring groups to working alone or having a serious side versus a lighter side). By your early 20s, your personality traits have stabilized and won’t change. How you behave is driven by your personality and by a set of skills called emotional intelligence (EQ) that you can acquire and develop throughout your life. By using EQ skills, Jane could have chosen a better response to her direct report that wouldn’t have jeopardized her career.