I turned around at Bright Angel in the Grand Canyon this Winter. Despite being real bummed about it, I headed down Hermit's Rest which gets more sun and was no longer icy.
"Oh well, I'll settle today" I thought. Midway down Hermit's Rest I cross a much more experienced hiker -- she had lived in and around the Grand Canyon full-time for a year. She was only coming back to the Rim to move her car due to the incoming on-season (yeah, just a "casual" river to rim and back, lol). She told me she had just been around Bright Angel the day prior and had seen a girl be air-lifted away with a broken leg. Even though she had microspikes and months of winter experience in that park specifically, she bailed.
Suddenly, I didn't feel like I settled anymore... turning back can save lives and limbs. The majority of the time, nature (and the trail) will still be there when you return. It will certainly outlast you, if anything.