Some people are unlucky enough to have to do the long day after the induction programme. Your first experience of a brand new way of working, and it's after hours. I had this experience recently. I had to get venous access and take pre-op bloods on an incredibly cute four year old who was having her tetralogy of Fallot repaired the next day. Cardiac kids have no veins. They're famous for it.
It doesn't stop you trying though. I aimed, I entered the skin with the needle, I probed, she cried, I hit something and got a little bit of flashback (blood brought into the end of the cannula through suction, to let you know you're in a vein), but couldn't advance it. She cried more. I took it out eventually, after she moaned and moaned and moaned that this was what she wanted, and held some gauze on her hand (which, of course, was now pouring with blood - they like to do that when you've been unable to get the cannula in).
I looked really sad at her. It wasn't a hard look to muster; I hate missing with cannulas, and I hate putting kids through unnecessary trauma. Evidently, this sad look was pretty convincing, as she looked at me, then launched herself forward off the bed and gave me this really big hug.
I'm lucky. I get to do some pretty amazing stuff at work. Sometimes, though, the thing that still makes you smile at the end of the day is the tiniest little thing like a spontaneous bit of comforting from somebody who has every right to be upset with you.