Dealing with ignorance, and arrogance?

I lived with and dated a girl who worked as a manager for a child entertainment center(Kind of Like Chuck "E" Cheeses) for 2 years. She pretty much was a slave for her job working 7 days a week, and even if she did have a day off she still somehow incorporated working on that day off. Pretty much her life consisted of working, getting her nails/hair done with her best friend, smoking cigarettes, and hanging out at the mall. Not much else to the lifestyle. Anyways her co-workers, boss, her mother, and best friend bashed me and kept egging her on to get rid of me. Also, these people always tried to be very competitive to out do me, put me down, or make themselves feel better. One thing led to another, she cheated on me with a co-worker, and also another guy friend and dropped me. I had to move out as I was not going to live with somebody who disrespected and rejected me. All the while trying to make it look like her friends and herself were better than me. Keep in mind this ex girlfriend does not have a college education, can't pay her bills, and constantly complains to her mother everyday on the phone. Myself I'm college educated, was making better money than her, and always treated people how I always wanted to be treated. Thats not to say I am perfect, or better than her or am arrogant. I feel as though they underestimated me, and had to put me down constantly to make themselves feel better or important. I don't know why or how somebody who manages a glorified daycare center can feel like she is Donald Trump or Meg Whitman of Ebay. Anyways since then I went back to school to get a graduate degree, and switched to a career that was more skilled, pays better, and more glamorous. I also don't really see what this guy who she left me for has over me. He's 30, rides a Harley, has his nose pierced, has tatoos all over his body, has a drinking problem, and works for the gas company as a laborer. Again I'm not saying I am better than him, but I know I am of a cleaner caliber than he. I guess my question is, how do you deal with people who try to put you down, try to out do you, and make you feel inferior to them when really they aren't any better than you?