Not climbing but...
When I was 19 a friend and I went out to ski Mt Herman on a day with considerable avalanche danger. We were young and eager. Ignoring natural avalanche activity on the way up, we stuck to our original plan of skiing down the trees on the skiers left side of the main gut on the south east face rather than skiing back down the skin track like we should have. When I dropped in to the gut I cut off a thick wind slab that swept down all the way to the valley floor.
Unbeknownst to me, my friend and local hardcore, Woods was boot packing up the gut solo at the time that I triggered the slab. Woods was taken by the slide, carried several hundred feet and somehow with incredible luck swept out onto a bench where he stopped. Fortunately he was uninjured.
That day I learned that if you do not adjust the plan based on observations or if you don't allow new information to factor into your plan you can get killed or get your friends killed real fast.
Fortunately, I haven't had a total near death epic while climbing but I can think of some other scary and humbling moments in climbing that perhaps I will share later.