Actually I know I am 
Moved to a new area last year, and went to a new playgroup to try and make friends with DD1 (2.5) and DD2 (5 months). It was fantastic, friendly mums, great equipment, well run, I was in heaven. At the end we all sat down for lunch on the floor with our kids - about 15 mums and 20+ children. I realised I had left DD1's sippy cup in the car, which was just outside. I turned to the lovely mum next to me and asked if she wouldn't mind watching them for me while I ran to the car. She said yes.
...I know, I should have taken them, but DD1 was 2.5 and would have had a shit fit to be taken away from her lunch, and I thought, I'll only be 30 seconds...
I ran out of the room, pushed open the heavy door to the foyer, straight into a toddler, who fell over and started screaming, proper 'I'm in agony' screaming. I was mortified and apologised and apologised. The mum couldn't have been nicer about it. I got to the car, grabbed the sippy cup, and when I got back into the foyer, to find she'd taken his sock off and there was blood EVERYWHERE. I had split his toe open with the door.
I was beside myself with horror and the sainted mum just kept saying, 'he'll be fine it was an accident.' Then I heard more screaming...
Both DD1 and 2 had cottoned on to the fact I wasn't there and had both had screaming meltdown fits while poor lovely mum did the best she could and they teated her like some kind of evil mummy stealer. I walked back into the room to find 15 pairs of unsurprisingly judgey eyes staring at me, blurted out "there's blood everywhere and it's all my fault" and then burst into tears myself.
It took about 5 days for me to stop chewing my fist night and day with horror over that experience.