cold and deadly is how you react to flies, don't let them addle you, just slowly, calmy move to them when they are stupid enough to pause, get real close then SLAM done... then if you miss, pause, breathe, wait for them to pause again, etc

they are just dumb as fuck, really sucks getting irritated over it, i know... i wish i could squash the chihuahuas the same way that constantly disrupt the peace