For me it was while hiking. It got dark but I wanted to find some nice camping spot so just kept walking. At one point the path got really narrow and pitch black on both sides but I never saw anything remotely dangerous in those mountains so I just kept walking. After some time it got a bit more vertical but I still couldn't see anything dangerous so I just kept traversing it. Then one hold broke off and I fell backwards, landed on a small ledge half a meter lower and just stopped. I decided it's getting silly so I just found small flat surface and slept there. In the morning I saw were I was and the slope where I almost fell had like 50 meters and was almost vertical. I really don't know but I think if I didn't stick the first small fall I wouldn't be able to stop until the very bottom. 50 m rolling down a rocky hill, alone, in the middle of no where. Yeah, I would probably be dead. So it was couple centimeters really.

Later I learned that this spot is pretty well known: https://www.youtube.com/watch?v=3zGhS3-KVuo