Your particular situation is not enough to assess the safety of fisting. I could also say "I smoke and have no cancer, therefore smoking is safe". Would it make sense? No, because one specific case doesn't prove anything. Otherwise, researchers in the medical field would not bother conducting studies on thousands of people, they would just take one person and draw conclusions. You can fall for logical fallacies as much as you want, but try not to give health advice to other people based on those fallacies.