I think that's a worthwhile question and it has nothing to do with Winter. I've wondered about it myself for a long while, coming to the conclusion that we live in cynical times, made even more so by the incessant bombardment of "information" from various media and the non-stop movie of images we see daily, on billboards, our TV, the Internet, in magazines and so forth. Desire is being manufactured on our behalf for things we do not want and certainly do not need, and often cannot afford, by people who want us to think otherwise; gossip poses as news and most of the actual news we get is biased in one way or another by the time we receive it. As well, there is the relentless media reminding us of a recession, a war on terror, inane political squabbles which won't matter at at all a week from now but are presented as earth-shaking events. Couple those things with celebrity worship which holds out images of perfect teeth and perfect bodies and beautiful faces most of us will never posses and we seem less worthwhile in comparison. All these things conspire to create a frame of mind in which we feel we are lacking something and in need of something we can't obtain. So, sometimes we get grumpy.
In other words, I think there are a lot of cultural forces at work undermining any real chance we have to be happy. In the end, though, you have to laugh.