I know a lot of words. I don't know all the words, but my vocabulary is larger than the average person. Some people think this is an impressive thing, and for a while I believed them. I thought that somehow I just knew more words than people. But I have realized that it is not that special.
I am no different than any other person. I grew up knowing nothing and picked a lot up by listening to people around me. I came across plenty of words I didn't know. I still come across words I don't know. I had no idea what "stultify" meant when I read it today.
The only thing that sets me apart from many is that, when I read that word, I pulled out my dictionary and looked it up. Now I know what it means. I have a new concept to use and I have expanded my vocabulary by a dozen words or so (because I know 'stultify' and 'stultification' and 'stultifier' and every other form of the word).
As a writer, the larger your vocabulary, the more accurately and succinctly you can express yourself. Every time you see a new word, don't shrug and move on, take the time to acquire it.
P.S. If you are scratching your head wondering what the heck "stultify" means, guess what I'm going to tell you to do.