I was on a day hike with some folks I had just started working with. It was a semi-sanctioned team building exercise at a camp I was working at. Our fearless leader (Activities and programming director) had done the hike before, so had a good idea of what we needed. Or so I thought. The goal was to crawl a small cave, which was rated by him as fairly novice, after an easy two hour hike. The hike turned into three hours... "Oh yeah, we brought bikes the last time I came up, so we were able to get to the actual trailhead much easier" The first hour was a private blacktop road, not fun for the feet. Then two hours up what I would call a moderate hike. This should have been another clue that something wasn't right. While most of the group was doing alright, myself and one of the girls (now my wife) were having trouble. I'm in decent shape, but the rest of the group were natural athletes, and my hiking partner had just left university, so hadn't gotten back into out of school shape. We paused for a breather at the cave mouth, and were told that we were behind time. again, a bad sign I missed. Bad thing three hit five minutes after that, "there is way more ice in the cave than there was last time" We were fairly well equipped, coveralls, helmets, headlamps. But no one had a backup light they could carry, and the token mountaineering gear got left at the cave mouth, since there would be no way to drag it along. First squeeze, no problems, second squeeeze, bit tougher and a bit wet, but nothing major. Never in my life have I been in dark like that. the room was the size of a stadium, or so it felt. Third sqeeze, everyone buddies up, the leader and the possibly insane salvage diver are a pair, followed by the two type A hyper competitive sisters, leaving myself and a girl I had barely met to bring up the rear, (neither of us had caved before) the third squeeze was a nightmare. the shelf we had to crawl down was about half a rib-cage wide, covered in ice, with about a foot gap to the opposite wall, over a very deep chasm, full of water... I have no idea how far in we got, I'm guessing that it was maybe 12 feet, maybe a bit more when we heard from up ahead that both other groups were in the next chamber. At this point, the muscles are starting to lock, my partner has said nothing for far too long, and the water has gotten through everything. I'm a very low R-value type human, so when I run out of energy, I get cold, fast. First shiver... oh sh!t. So I called ahead that we were going back. I have no idea how we turned around, but some how were able to shove each other back out of that crack. Next problem, where is the door? We made it out, but in the car after double-timing it down the mountain (including one minor fall which could have ended very badly, due to the fearless leader guiding someone with no mountain experience down a scree slope in a rush) we found out just how badly the leader had miss judged that trip. we made it back, but he had a bit of a rough summer, given that he was supposed to be my boss, but there wasn't much trust left....
Hell of an experience, looking back I should have pulled the pin earlier, but I had trust that I could do what he said I could do. Now I pretty much don't listen to people who try to tell me what my physical capabilities are.
I've gone on other trips since then where things have gone a little sideways, but its all about your acceptable level of risk. Also who you are with, I've had other trips go pretty wrong, but I wasn't worried due to my traveling companion, I knew that we can work together and get it done.
Sometimes its about heading back to the parking lot, sometimes its about pulling the car over for a sleep. Any plan might need changing so its more about the situational awareness of re-evaluating your goals and plans as conditions change.
I try to have as many things in place day to day to adapt myself as much as possible. Part of that is I really like being comfortable. I hate being cold and wet, I hate being hungry or thirsty, or over-heated. So yeah, I could just suck it up, or I can carry a towel, water bottle, granola bar, and hat. Sure its a bit of a chore to carry stuff around every day, but to me its more than balanced out by the number of times a day has not gotten worse because of something I brought with, so I didn't have to change plans, Or so I had something available that opened up other options, for when the plan changed without me.