Like someone else said, med errors are going to happen. No one is perfect. You're bound to make a mistake somewhere down the road...thankfully, the ones I've made haven't been serious. If you check yourself like you're supposed to, you should be ok.
Oh, and med error includes ANTHING to do with meds...not always giving the wrong med to the wrong patient. It could be giving the right med to right patient but at the wrong time. Or, if an order wasn't taken off to decrease a med (or increase it)...that would be a med error.
But, use common sense. The other day, on one of my resident's MARs...an order read "give 220cc of ferrous sulfate"....that's quite a bit. It should have read 220mg (which would have been 5cc). Thankfully, being a little bit of a 'seasoned' nurse (5 years), I knew that 220cc of Fe was quite a bit and knew to check...but, I worry if a new nurse would have read it, which is where the common sense, hopefully, would kick in.