A woman who was earning $500,000 a year by 30 shares the biggest mistake she ever made with her money

Cary Carbonaro was earning $500,000 by the time she was 30, but that didn't make her immune to making some poor financial decisions.

As Carbonaro writes in her book,"The Money Queen's Guide: For Women Who Want Build Wealth and Banish Fear," she made one major mistake with her money: She allowed her emotions to control a major financial decision.

During her divorce, her husband ambushed her with 100-page Marital Separation Agreement that she signed under duress.

"I literally gave away half of what I earned and half of what I had worked tirelessly to build," she writes. "Through my signature, it was his."

When Carbonaro married her husband in 2000. "He was what I wanted and, on paper, it was a perfect merger of equals," she writes.

But that didn't turn out to be the case.

Instead of sharing the financial responsibilities, Carbonaro ended up taking on every cost, putting bills, mortgages, and loans in her name. Her husband told her his money was his alone, and was "unavailable" for paying bills.

"I had no idea what I was in for," Carbonaro writes. "I was open, vulnerable, and trusting, which made me the perfect victim."

After her divorce, she found herself in the red for the first time in her life. Luckily, she had an emergency fund and was able to get through almost four years of negative cash flow.

She writes:

Inevitably, at some point in your life the line between personal decisions and financial decisions is going to blur ... this was definitely a blurry a time for me. The emotions were heavy and real, and they made it that much more difficult to see the forest for the trees, as the saying goes. This dichotomy of the head and heart is the root cause of many poor financial decisions, and I was not immune.

After years of struggle and personal development, she got back into her work and became a certified financial planner to help others avoid similar mistakes. She uses her personal trials as examples and learning experiences to help others.

"I began to take a very reflective and strong look at my life," she writes. "I lost hundreds of thousands of dollars because I couldn't see that my emotional relationship was manifesting bad financial practices in my monetary relationship."

Now, she encourages clients to save money starting at an early age, to cushion the blow of any potentially emotional mistakes just like her emergency fund kept her afloat after her divorce. "It is not just about avoiding emotional landmines as you age," she writes. "It is also about being able to recover if you do step on one."