Or just that they'll mean different things than how you understand the terms now.
And I can't understand how someone can like bananas. This doesn't stop me from acknowledging that some people do.
As a starting point, try thinking about what the foundation of your current views on gender identity are.
Sex isn't gender, but one thing that helped me broaden my understanding on the issues of sex and gender generally was to recognize that intersex people are as common as redheads. If our view of gender is based on this idea that gender is a clear binary that perfectly corresponds to a clear sex binary, well... it's settled biology that there really isn't a clear, inviolable sex binary, so the whole paradigm is based on false ideas.