First Medication Error.....feeling horrible!!

I have been an RN since May of this year, and work on a general surgical unit. Last night, I had 8 pts, and was working with an LPN who had 8 as well, so had to cover all her IVP meds and other parts of her charting. We had 1 CNA. At the very end of my shift, I gave 50 of lantus insulin to a patient without looking at the MAR BuT verifying the amount with my supervisor because I was way behind on EVERYTHING and was used to giving her insulin in the am. I realilzed it about 10 min later when going back to chart on the MAR. The BS was 112, and I immediately told the supervisor and called the dr. He didn't seem concerned, just said to monitor her BS and give her D50 if less than 70. It was end of shift so I had to pass the pt on to day nurse and I felt AWFuL!!! I cried, and everyone was so supportive, telling me she'd be just fine, and she'd be closely monitored and treated if she wasn't. She was a knee replacement, and was due to go home today. I didn't get to eat anything all shift, and its now 830am and feel nauseated from my stupid mistake! This is my first EVER med error. How do I get over it? And how do I get myself to go back to work tonight??? I just want to quit and run away! I know I SHOuLD feel awful, and I KNOW I'll learn from this, but I'm feeling very alone through it all. HELP!!!