During 22 years of military life I tried many things to help me adjust to unpleasant conditions around the world. One thing I discovered early on was that one small candle can heat a surprisingly large area if you can find a way to contain it. I used to drape a poncho over a folding field cot and put a small candle or tea light under it. As long as you can keep from having a draft under the cot you can sleep toasty warm, even in sub-freezing temps.
I once moved into an apartment and had to wait a few days before the electricity was turned on. A few candles placed in front of mirrors helped for light and warmth.