Not minimizing yourself at work is very important for both men and women. I worked with a project manager ( a guy) who was very good at his job. I liked working with him, more than most project managers. One day, while I was at lunch I heard people who didn't work with him criticizing him.
He had a habit of qualifying every question he asked of the technical folks on the project. He used phrases like:
"I don't know too much about "X", so maybe this question is kind of 'out there'...
"It seems to me that, x and y, means z, but what do I know?"
and so on.
The next meeting of his I went to, he started minimizing himself and I rolled my eyes. That was bad of me, I know, and it even surprised me that I did it. He noticed, and, after the meeting, he asked why I had rolled my eyes.
So I told him what I had heard (not who said it), and I explained why I thought they were saying it.
To his credit, he took the eye roll and my news to heart, did not get angry with me, and I never heard him minimize his own knowledge again. About a year and a half later, he was promoted and was well respected. All that had changed was his personal presentation of himself.