There are so many but here are some good ones.
I repaired a trail map which was torn and frayed on one of the seams.
My friend and I went hiking and on our way out we were checking the map to see if we could find a different route just for the sake of diversion.
We picked one and had a brief discussion about why we have never observed this trail as being an acceptable route in the past.
For no particular reason, we decided to use our old standby route.
When I arrived home, I checked another map of the area and came to the realization that had we followed our "new" trail, we would have walked for many miles, only to end up in a place where we most certainly did not want to be.
I usually do not tape up torn maps anymore and if I do, I am neurotic about where the lines are.
Another one. On both Mt Equinox and Smugglers, I hiked up in new boots and dismissed the pain I was having early on as insignificant and kept on hiking. By the time I summited, I could hardly walk. Coming back down was truly the "descent from hell". Really bad raw blisters!
The lesson: don't take your brand new boots up a mountain the first time you wear them. If you start to have pain, stop and try to pad it. Abandon your climb if the pain is worsening because it's not going to be cured by summiting. It will only get much worse and set you up for a more serious injury. Make sure your first aid kit has moleskin in it.
One more....
I had a bad case of plantar fascitis and was treated with cortisone injections by a podiatrist. He warned me that under no circumstances should I climb Mt Madison for my BD hike. My feet were feeling pretty good so my friend and I forged ahead. I was really suffering the next day when we were coming down Watson Path. A nasty little trail as I recall it. Much to her dismay, she had to take my pack. Excruciating pain all the way back.
The good doctor told me that essentially what I did was the same thing as if I tried to walk on a broken leg. The really bad thing was I new this was happening on the way up but refused to succumb to a "little" discomfort. I was desperate to climb Madison and sleep in the hut. Full moon night! It took months to get that healed.
The moral to the story is: heed the warnings when they say "only those is top physical condition should attempt this trail".
Last but not least....
I climbed up Mt Pierce with a friend for a day hike. It was rainy so the trail was a bit slick. She had very little hiking experience. Came time to come down so we left the hut and moved right along. I was in the lead and we went right past the cutoff and down good old Webster Cliff. Now I noticed early on that something was not quite right. I finally mentioned to my friend that I did not think we were on the right trail. She was adamant that there was no problem because she "recognized" the terrain, even specific trees. Finally, after I took a bad fall down some very slippery rocks and injured my knee, I checked the map and discovered what my gut had been telling me right along.
WRONG TRAIL. Fortunately, a thru hiker came by and this trail angel ,"Chestnut" took my pack so I could crawl back up to Mizpah Hut. The sun was setting so we would have been benighted if the "Chestnut" had not happened by. Bring enough gear to spend the night in the woods. You just never know what's goin' to happen. It's a good idea to pay attention to trail signs and junctions to. We were so busy talking, neither one of us saw it and listen to your gut!
I did learn my lesson. Last fall I was in VT on some dirt roads with a friend and trying to find my way out.
She assured me she was very good with maps. With great enthusiasm, she started pointing me in the "right" direction. I decided to take a closer look and sure enough. She was holding the map upside down