When ds1 was at the just-crawling stage, I left him downstairs whilst I nipped upstairs for a wee. He was in the dining room which was open plan to the kitchen, but everything was babyproofed, so I thought it would be OK.
From the bathroom, I heard a baby crying outside - Oh, thought I, the neighbour's must have a visitor with a baby - and then I thought nothing more of it, and ignored the wailing while I finished my wee and washed my hands.
When I got downstairs, I found ds1 wedged halfway through the cat flap. He'd tried to go out with both arms over his head - as if he was diving - and had got totally stuck, unable to reach anything to pull himself out with his arms or push himself out with his feet!
The only way I could get him out was to open th back door (very carefully so I didn't smack his head off the wall) and essentially deliver him into the garden!
When he hit the tantrum stage, during one truly awful screaming fit, I was on the phone to dh when ds1 stopped crying. When I went to see why, he was at the kitchen bin, eating tortilla chips dh had thrown away the night before.
I looked at him and I knew, just knew, that if I took him away from his yummy snack, he'd start screaming again, and I couldn't face it - so I let him carry on eating until he got bored and went to play with his toys!!. I did then move the bin to somewhere more secure.
Ds1 is now nearly 24, and has a degree in law and a full time job, so I can't have done him too much harm.
We all make mistakes as parents - we are human.