I once took care of a little old lady in the ER who had a SBO. I was a big time "sympathetic puker" . Boy some one starts to vomit, I start to do the goose neck thing. Well this little old lady was vomiting stool. I started to gag praying I did not spew. The little lady was crying saying to I'm so sorry.
I felt so bad I stopped gagging and put my arm around her and thought, "No, I am the sorry one." That night I got over it. no trick, just got over it.