How can I avoid sounding condescending?

I have recently been informed that oftentimes I come off (unintentionally) as condescending. From what I can get out of people who know me, I sound like I have a superior attitude and that I am “smarter than everyone else”. After looking on other answers I saw the recommendation to “match vocabulary” with the person you’re talking to, but I’m not sure I can do that. It is a habit of mine to use non-typical words (not because I’m trying to “impress” anyone – that really is just the first word I think of) and I’m not sure how natural it would be to use everyday vernacular. Do you have any suggestions on this or any other tips you can think of? Also, please give me any information you can think of on what causes you to consider other people “condescending” / “patronizing” or “b*tchy”. Thank you very much for the input!