Schedule daily debriefings.
If you are surrounded with folks who like to list your character defects and have made a pastime of making you feel bad, you are going to have to schedule some “reality checks” throughout the day, where you can make your own list of character strengths, and why you are actually overqualified for this dinky little job. If you can’t make that list, then make a self-esteem file, where you ask friends to make the list for you. I suppose it’s like being exposed to a cult — after awhile you see everything from their point of view. However, if you are diligent about breaking out of that culture for a few times a day to remind yourself of your own personal values, you are less likely to be sucked into the group philosophy.