You'll Be Freezing
Have I mentioned you'll be freezing? While getting into bed is painful, once you're wrapped up in your sleeping bag, you'll probably end up peeling off a layer or two in the middle of the night. I usually went to sleep wearing two bottom layers, one pair of thick socks, one top base layer, a heavy sweatshirt, a down jacket, a winter hat, and gloves. I had a North Face Furnace Sleeping Bag ($179), and I usually took off the down jacket and sweatshirt during the night.
Most tea houses also give you a thick blanket on your bed, but we usually had to roll them up and use them as pillows since the ones provided were super thin, and keeping your head elevated is super important to help prevent headaches.