Can you bargain? Is it a skill anyone can learn?

You always hear the stories or may have experienced yourself dealing with an aggressive salesmen, I know myself that I could never haggle with a salesman for a few reasons, but I know it’s a good thing to do because it my money right? If you are a great haggler, how do you do it? Is it a certain mindset you have to be in? Were you just tired of getting screwed over?
How do you keep up with the mentally draining mind games?