IV fluid mishap...worried

So I've been having stress issues at work lately, the amount of work is starting to get to me, and I dread going there by the end of the week. So yesterday I came into work and the regular dayshift nurse hadn't called in any of the labs, one of which was stat lab for a patient with declining health that I had ordered the previous day almost 24 hours later. I called the doctor and they wanted an IV started immediatly because the patient was very dehydrated, the order was for D5W. For some reason my memory lapsed, and I grabbed D5NS instead. I just realized my error when I woke up this morning. This is only my 3rd IV on my own since nursing school, and now I'm freaking out wondering if that could have hurt the patient and if I'm going to get fired. I'd checked on this patient every half hour, and by the end of my shift half the fluid was gone and his blood pressure was within normal limits. Has anyone else ever had a dumb moment like this, and if so what happened?