I've been trying to fall asleep for 3 hrs in a sleeping bag in the middle of a dark forest together with ten other persons in a tent. It's close to zero degrees celsius outside, but we have a stove with a chimney in the tent, so it's warm. This might sound a little crazy, but in my age living a middle class life I don't want to get too comfortable, so I need to challenge myself. My grandparents were fighting the mighty Soviet army in The Winter War during WW2, in record cold winter with -40°C, to protect the independence of Finland. There are not many hardships that can be compared to that.