I take pride in toughing it out, sitting for long hours on stand in very cold temps. that put most guys at home. I think mental toughness is a big key, dont keep thinkin your getting cold, and have things to look forward to, like your snadwich or snacks spaced out at intervals through the day. i have actually hunted in cold temps and stood all day dark to dark( yes stood, stand did'nt have a seat) eating a good breakfast is very important, high in fat and protiens, and the foods you take with you should be the same. take enough food to keep you happy, and make sure you drink.... to may times the cold makes you feel as if your not thirsty but you need to drink.
Also if you feel you need to go to outdoor bathroom, weather to pee or a #2 you should not hold it for to long. i have noticed when i need to go and hold it i get colder and i actually warm up after i go. dont laugh try it for yourself....
next to your skin you want no cotton or materials that are cold like underarmor cold gear or heat gear. its good for walkin but not sittin you want clothing thats soft and warm like a wool blend thats higher in wool than whatever else is in it, then polypropylene or like the polartec. the next layer shou be something fleece like so when your underware wicks moisture it easily gets drawn through the fleece. cause your body heat and the nature of fleece will dry off very fast. over that stuff i usually put heavy wool sweaters or a good material with loft to trap your heat. i also alway wear a good warm vest, it adds insulation without bulking up your arms. your outerware needs to break wind, cant stress that enough the cold goes through you or draws heat out your done! and usually bibs are warmer than pants... i keep away from jackets that have tight waist band cause they will ride up your back and not alow your under layers to lay properly and will bind or ride up. keep all your clothing loose fitting to trap dead air space and also to not feel so bound up wearing all the clothes.
keep your neck and head covered, all times. and no cotton here either its cold against the skin, wool, fleece or something similar and its better to have somekind of windbreak in it too. make sure its tucked down into your jacket. you loose most your head through your neck and heaad so its very important to keep them warm, covered! your hand shoud be kept warm same as your head. if you need to wear thin gloves use the chemical hand warmers and or have one of the muffs that the football players wear on the field.
pac boots are the best, with the wool liners or heavy thinsulate boots, that are a little large. you need to have room for good heavy wool boot socks and the chemical warmers if needed. if you use the chemical warmers i had better luck putting them on top of my toes instead of on bottom. and when you get to your stnd loosen up the laces on your boots to alow better circulation to the foot. also i use a over the boot cover that called ($20)ThermalFeet... they cover just the toes and are very light to carry as compared to the full boot covers, and you can also put the hand warmers in those as well. they have saved me and added hours of hunting time for me by useing them when my feet start to get cold.
alow ample time when walkin to your stand and take breaks to avoid getting sweaty. pack most of your clothes in a large back pack to keep you from sweating... i aslso find myself hunting from ground more to cause it alot warmer than in a stand, make a ground blind so you can keep your movements from being seen and help block the wind. i have also found it warmer to stand than to sit all day, or just use your chair when your legs get tired, make sure your chair dont cut off circulation to back of your legs as well.