I tried to write an article on this topic, and I went through a number of drafts before shelving it. I even asked for input in the Instructor to Instructor forum, and even the very good ideas I got there did not get me to my goal. Where indeed does one draw the line? How can you tell when you are going past your limits? Here are two examples of a similar decision by two widely different individuals.
Agnes Milowka was a celebrated cave diver famous for taking what many people thought were unnecessary risks. Her web site, still up years after her death, celebrates a moment she nearly died. She finally did die trying to extend the line on a cave system in Australia. She found herself in a situation where she could not fit through a restriction with her sidemounted tanks, which is saying a lot because she was most famous for wriggling her petite frame through seemingly impossible holes. She therefore removed one of her tanks and went through with just one. She was unable to get back in time to the one she left behind.
In contrast, I am not remotely celebrated for any diving accomplishments. While we were planning a wreck dive to a little deeper than 200 feet max, my buddy suggested we swim through a hole in the bottom of the hull that was made when they blew the charges to sink the wreck. He had heard it was a really good experience. The only problem was that we would not be able to fit through while carrying our decompression bottles. We would have to leave them outside the wreck, navigate through the wreck and out an upper deck in order to get back to the bottles before beginning the ascent. Nope! I would have nothing to do with a plan like that. That is not even close to the level of challenge Milowka faced, and the odds that we could get back to our bottles were excellent, but those odds were not good enough for me. Maybe someday I will be willing to stage my deco bottles under those circumstances, but I was not there then, and I am not there now. I stage bottles in a cave without giving it a second thought, but that is because I know I will be coming back that way again, and if I don't, the loss of those bottles will be the least of my problems.