Well, youre opening question is a laugh-out-loud one, so I feel obligated to help.
First of all, youre probably sweating more during the day than you think. But because youre moving around, the sweat has more chance to evaporate. At night, in a still room (or tent), you may be more apt to suffer from the wet stuff. I know that I can often be very comfortable walking around on a warm night, but the minute I go to bed I feel too hot and start to sweat.
That said, you may suffer from sort of night hyperhidrosisaka, night sweats. This is a real medical condition, and if you havent consulted a doctor about it, you might consider doing so. The body temperature of most people drops late in the evening, and your thermal-regulating system may be out of whack. Sleep apnea is fairly commonly associated with nighttime sweating.
Anyway, in your case, I wouldnt get into the sleeping bag without some sort of layer over myself. This is a good practice for most people, as your bare skin next to the bag can quickly dirty the liner, meaning the bag will need to be laundered more often, which can shorten its lifespan. I like Patagonias silkweight Capilene, which is now called Capilene 1 ($36 each for T-shirt and bottoms; www.patagonia.com). Its very soft and comfortable, doesnt add too much insulation, and is very good at helping skin moisture evaporate. Alternatively, a bag liner such as Cocoon Silk Bag Liner ($60; ww.rei.com) does much the same thing and doubles as a light sleeping bag/blanket.
So try that, and maybe consult with someone. Youd be much happier dry at night.
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