One thing that makes me suffer is climbing into a cold headwind, freezing and sweating at the same time.
Once we rode over the local mountains when I had tonsilitis and was pretty sick. I only had a worn out wool jersey, no hat, no vest. After a 7 mile climb into a strong headwind, they waited for me and they said I didn't look so good and was very white. I finished the ride and actually felt a lot better after that climb was over. I've done stupid.
I used to scout routes for mtb rides by myself. Once I had the route figured out, I would round up the homies and we would do it. One cold windy day I bit off a little more than I should have and was miles from a road or anything and ran out of food and water. A guy came by on an atv and gave me some water and told me how to get out of there.
Once I picked a route from a map that I had only done part of myself. I dragged some friends along and the map didn't mention the trails were washed away and we had to walk a lot of it. It was dark by the time we got out of there and getting pretty cold. The homies were not amused.