Last winter, my wife and I went to Ashland, Oregon (I wrote extensively about it here). I was somewhat surprised recently to read that I had a reasonable amount of neck pain the first couple days I was there. Looking back now, it's like I didn't actually experience the pain, my mind seems to only want to remember the good things about the trip.
This is most likely a universal experience. So when we think that some past event was such an awesome time or that days gone by far surpass what we're going through today, most likely we're remembering the way it never was. Something to keep in mind the next time you get wistful for the past (though there's virtually no question that the Clinton years were the best of all times in which to live).