I never thought about Imodium, but in BJJ there's another remedy for an uneasy stomach that's relatively common in jiu-jitsu circles, which I don't think needs named haha.
I like to get ready for a match by watching my teammates matches. I'm usually more nervous for theirs than I am for mine. Mindset is also key for me when I compete. I don't go in thinking, "I need to kill my opponent!" I'm thinking, "My opponent is trying to kill me! How do I address that?"