Yesterday at work, I was taking the blood sugar on a patient and after putting the blood on the strip and waiting the 8 years for our ancient, piece of c r a p glucometer to read the results, it read "error" so I grabbed another strip, reset the glucometer and instead of poking the guy again, attempted to just squeeze out another drop from where I already stabbed his finger - BIG MISTAKE. The blood squirted out directly into my eyeball. I mean, it was a gusher. I had no idea that much blood could come out of a tiny pinprick. So, then I had to do the whole exposed to blood protocol and worry about getting diseases.
So, yeah, don't go squeezin' clotted off fingers and if you do, don't be an IDIOT and point them at your own face.
What stupid mistake have you made that we can all learn from?