For me personally, I find that my blocks on the words I struggle with are intensified when I remove the spontaneity element of it. As in, for example, when I dwell on how I might have to say a certain word in the future that I “just know” I can’t get out- it becomes a self fulfilling prophecy where it becomes even harder to get the word out cuz I keep thinking about it. You just really got to make the trouble words spontaneous if u need to say them, just don’t think about them. or u can always synonymous words that are easy for you; at the very least this helps regain your confidence and mental as it proves that you can still be a highly effective communicator that people want to listen to and care about. Hope this helped:)