When I was new, I had this wiggly, demented ole feller on a dopamine drip. It was a renal dose so there was a 250ml bag of NS hung for KVO. No problem. The dopamine bag was also 250 ml. The pump alarmed, a bag was empty, (no we did not have scanning or such at the time) I said "oh my dopamine's out" and went and got some.
I stopped the pump, stood there with a bag in hand, unspiked it, opened the new one, and the patient moved or something, while I was busy thinking about the pump that the line ran to and how the rate just sounded "off" for dopamine, causing me to drop the full, open bag of dopamine and spill it on his bed. Then I realized it was the NS that was out. Pharmacy was very nice when I explained that I hadn't hung it, but was gonna, could they not charge it to the patient please, it's wasted in the linen.
I felt so bad that I nearly cried; but hey, the patient got a bath, he didn't get triple his dose of med, he never knew, honestly, that anything was wrong. And I got this new habit of triple-checking just when I'm about to hang something. It's no wonder we're OCD as all heck- we develop these habits before and after we make mistakes. Relax. You did something wrong, and you learned, and it won't be the last time.