"If something works one way one time it'll often work that way other times. You just can't start - cheating. I have denim because denim is nonthreatening. Denim doesn't antagonize faeries or gods or dragons. If I read everything there is to know about the characteristics of one of those things - if I could magically know about everything dragons have ever done in the history of always - and then I came up with a way to use denim to kill one without being personally staggeringly powerful such that it would be appropriate for me to beat a dragon, that seems like it would still make sense based on all that, then it might work, but only if the universe was in a good mood or if the dragon was due, and I probably couldn't do it twice."