I do not really understand it. In the Summer when the sun is bright and hot, having the shades all the way down makes my living room amazingly cool and comfortable. There are weeks when I leave the shades down 24/7. And turn off all but lights except those I really need to see.
In the winter, when the sun's rare appearance should make me feel warmer, it does not at all.
I do hate the glare of the sun when I'm outside - any time of year. It really bugs my eyes and gets in the way of my seeing stuff. And I do hate the heat of the sun. I was raised in the south before air conditioning was prevalent and I've done my time in too hot weather.
I used to like the sun's warmth in Winter and even spent my fare share of time sun bathing even, sometimes, in tanning booths. But the older I get the more sun averse I get.
I do get that my reaction to sun is not normal and kind of special snowflakey. I'm about 100 pounds away from turning into that little old hermit lady behind the blackout curtains.