Ex-Lehman CFO Erin Callan Montella shares her story

Callan: The pitfalls of a workaholic

She was one of the most important people on Wall Street — one of the top women in the entire financial world. But when Lehman fell in 2008, the bank's former chief financial officer, Erin Callan Montella, was dragged down, too.

Currently, the ex-Wall Streeter is warning women against the dangers of putting career success above everything else and sharing some of the biggest takeaways from her new memoir "Full Circle: A memoir of leaning in too far and the journey back."

"I think the book is intended to be an introspective reflection on my career, and I had to take responsibility for what I was doing in that position, at that point in time," Callan Montella told CNBC's "Closing Bell" on Wednesday.

"I wanted to take accountability for my own actions. How did I get there? Why was I in that place? It wasn't random. It wasn't chaos. It was all the things I had done up until then. And be clear with myself and with others about what I thought my role was," she added.

The title of Callan Montella's memoir is a not-so-subtle reference to Facebook COO Sheryl Sandberg's bestseller "Lean In," which encourages women to confront the obstacles they face in the workplace and challenge themselves in their careers. Callan Montella's book has been called by some the "Anti-Lean In."

The nonprofit LeanIn.org declined to comment.

For Callan Montella, "learning in too far" translated into sacrificing her personal life for success in the cutthroat environment that surrounds Wall Street.

"I really went through some very dark moments that I describe in the book," said Callan Montella. "I'm not proud that I didn't have the resiliency to get through it. The reason I didn't have the resiliency I hoped for is because of the way I had approached it, how much I had put into it and how little energy I put into the rest of my life."

The Harvard-educated executive was named a "Woman to Watch" by Fortune magazine in 2007 and "Lehman's Straight Shooter" by The Wall Street Journal in May 2008, and received other high-profile accolades.

Erin Callan
Source: NBC

One of her biggest takeaways? Traumatic events in your life don't always happen for a reason.

"Things will go wrong in your life, in your career," she said. "It doesn't always have to have a reason, but you can make it happen for a reason. You can take it and run with it, and make yourself a better person. You can make yourself a better employee. You can do something with that to improve your life, and that's what I've tried to do."

In March 2008, despite only having been CFO for three months, she was the only person from the bank on its conference call facing dozens of skeptical analysts.

Skinnygirl founder Bethenny Frankel attends the Skinnygirl Cocktails Launch Party at 620 Loft & Garden on February 10, 2015 in New York City.
One multimillionaire's advice on overcoming obstacles
Sheryl Sandberg
Do this every day, says Facebook's Sheryl Sandberg

"I've tried to take something that really wasn't so good in the end, and I've tried to make it happen for a reason and have a really different life and one that I truly appreciate."

Today, Callan Montella is married to Anthony Montella and has a daughter, Margaret Mary Montella. And she says she is happy with her new life path.