It depends on how your brain is wired. There are differences that can be observed between male and female brains that typically lead men to be better at math and women to be better with language, although there are always exceptions.
In addition, some people are visual learners and so do better with the Montessori methods of teaching math rather than the typical “write it on the blackboard” teaching method. Other people have other learning styles, some of which lend themselves to learning math and others that don’t.
Also, some people think themselves out of being able to do math. “Everyone” says it is hard so students may approach the subject with trepidation and then give up too soon.
All you can do if you fall into one of the “bad at math” groups is the best you can. Get tutoring, form a study group, find some small bit of math that you do understand and build from there, or plot out a career that will minimize the amount of math you will need.