I think the intended meaning becomes much clearer in the context of the preceding sentence: > I realized that I’ve overestimated my ability to quickly understa

I think the intended meaning becomes much clearer in the context of the preceding sentence: > I realized that I’ve overestimated my ability to quickly understand what drives people to do what they do. I have overvalued reasoning in myself and others and undervalued pride, fear and the need to belong. The context is "what drives people to do what they do", and she used to work on the assumption that what drives most people is mainly reasoning rather than emotions. But she discovered that this isn't true, including for herself.