FIRE can purify water, cook food, signal rescuers, provide warmth, light and comfort, help keep predators at a distance, and can be a most welcome friend and companion. Each and every person who ventures into the Outdoors should have a minimum of two ways to start a fire with them, one on their person at all times and the other with their gear. A few small fires provides more heat than one large fire. Collect firewood you think you will need for the night and then collect the same amount again, experience shows you will need it. Anything that takes away or adds to your overall body temperature can be your enemy.
Clothing is the first line of shelter protection, have the right clothes for the right environment.
Always have a hat. Try and keep the layer closest to your body dry. Layers trap air and are warmer than one thick garment. Do not expend energy making a shelter if nature provides one. Practice building a quick lean-to shelter in case you can not find your campsite, do not wait until you need to make one.