With a few and occasional exceptions, we are accustomed to how we sound when we talk. We travel with friends and family and their language patterns and sounds are familiar to us. Once in a while we run into someone who wants to know, "Where are you from?" They know we're not from "around here" because they hear it. Its in these transitions of life that our language trips us up and often we don't even know it.
For example, in a job interview, our language reveals that we have at least two standards for people in general: male and female. Human Resource personnel must try to hire the best people who will be the best fit for their organization. They will be listening for not only what you say, but how you say it. They don't want to have any problems within their organization and some problems can be avoided by not hiring people who routinely speak of the opposite sex in a negative manner.
The person being interviewed is simply saying "what everybody knows and believes." Your language has given your position away and you may not get the position you want/need because you were unaware that people can and do read between the lines. It is very likely that you don't even know why the Human Resource Director decided you weren't a "good fit" for their corporation.
The fear most employers have when they hear bad language is missed or misinterpreted communications on the job. Grammar is the method we use to control the number of possible interpretations of what we are saying. If our grammar is sloppy the outcomes may not be predictable.
The folk we travel with most of the time probably are not viewed by us as having an accent. Its only when you get out of your usual environment that others say, "Where are you from? I think I hear an accent in your voice." That example applies to many things, including the cultures in which we are raised. It certainly applies to the environment of most Human resource offices. The more aware of who you are and how you appear and sound the greater the probability that you will be hired.
There are some excellent resources available to you on job interviews. Take some time and begin working on this problem while you have time. When you're sitting in the interview it may be too late. (The links are just two examples of what is available to anyone interested.)