We never truly childproofed our house and DD has been going up and down the stairs since she could crawl up and down. She's 2 now and mostly walks up and down just fine with no help.
A little while back on a Saturday, she'd gone up to her room and I was downstairs cleaning. She often calls to me from her room or from the top of the stairs, and most times unless she needs something, we just talk and I stay where I am.
This time she was at the top of the stairs talking (can't see her, only hear her from downstairs) and something just made me stop what I was doing and go see her. I went up the 1st section and was on the little middle landing, she at the top holding a blanket, and she started to walk down, tripped on the blanket, and launched forward into the air. She literally turned upside down and was about to land on her head and I sprang forward and literally snatched her out of the air right before she hit. She still hit her head a bit when she initially fell, but no question, it could have been MUCH worse.
Obviously I was glad I was able to reach her before she hit, but what amazed me more was that usually I wouldn't have gone up the stairs in that situation. I'll never know what made me go, but I guess that gave me a super-mommy-instincts kind of feeling and I was feeling like a pretty good mom that day! :D
Nice thread idea, thanks for asking!