You're going about your day, when all of a sudden an annoying fly comes out of nowhere and keeps buzzing around your head. Your first order of action is probably to find your trusty flyswatter and then try to get rid of the annoyance.
But there's a problem - most of the time, you're going to miss the fly. Why?
Flies have a very fast sensory perception because they're so much smaller than we are. They transmit information much faster in terms of hertz, or cycles per second, and as a result, to the fly, we look like we're moving in slow motion.
If someone were moving in slow motion towards you, it would be super easy for you to dodge their every move, so consider this when you think about why flies are so hard to swat - it just so happens that you're easy to dodge because to them, you're moving very slowly.