thought I would share a bit of knowledge about how you lose heat aka get cold.
The five ways the body loses heat are
Conduction
Convection
Radiation
Respiration
Perspiration/Moisture

Conduction is the physical process where heat is lost because you are touching something cold. So don't sit or lay on the bare ground, a large stone or a snow covered log. Put some insulation between you and it. be sure there is good insulation between your sleeping bag and the ground. If you're hunting in Winter bring a 3X3 hunk of carpet with pad stapled together to stand on if your standing on the ground. Put some kind of pad on the tree you're leaning on in the treestand or on the ground.
Convection is the heat lost from the wind blowing over/around you. So putting it simply, stay out of the wind. Use self made and natural occuring windbreaks. Put your camp in the wind shadow of same as well as your stands. Wear a windproof layer if possible.
Radiation is heat lost just because your standing it the great wide open. Even though you are clothed well with a hat, a scarf, gloves, etc. The heat still radiates off you. It also radiates out of your tent. Having some kind of roof above you will help reduce heat loss from radiation. That is also another reason to put a tarp over your tent not just to keep the snow off your tent but to be a radiation inhibitor/reflector. I've never personally tried it but those treestand umbrella roofs might help in this regard.
These first three are why it is urgent to get yourself a shelter in a survival situation. A proper shelter will get you off direct contact with the ground, block the wind and cover you to hold in radiant heat.
Respiration is your own breath. You take in cold air and exhale warm, moist air. The faster you breath the faster you'll get cold. Control your breathing. Easy does it in activities in cold weather. I've never had one to try but one of those fairly new heat exchanger face covers might be a good investment for the Deep cold Season. Slow, steady work is much better than rushing, grunting and heaving in gulps of cold air. This also brings us to the last...
Perspiration or sweating...to put it simply, sweating can kill you. While exercise can heat up your muscles and warm you all over, you must not sweat. You should be dressed in layers against the cold, so if you're working, strip layers. If you sweat strip and dry yourself with a towel if available. Not just sweat but any mositure is lethal in the deep cold. Rain, slushy snow or falling into water are all potentional killers. You need to get out of wet weather or the water, and get yourself and your clothes dry just as fast as you safely can. You have longer than you think before serious hypothermia starts. As long as you can, and are shivering you're in the self save-able zone. If you stop shivering and get foggy in thought you better have a friend with you or immediate rescue. A word here on wool. Yes it can keep you warm when damp but it sucks up a lot of water if you fall in . The same is true for most synthetic insulation.
Try swimming in any of it. You'll find it is the most exhausting activity you've ever tried. Extreme care must be taken when walking on ice.
So remember whenever and whereever possible don't sit, stand or lay on bare ground or object. Try to stay out of the wind. Keep under cover. Control your breathing. Stay dry, stay warm, stay alive.