This isn't going to be a litany of the multiple possible reasons for that sadness, a method of making you feel guilty, or of enforcing thoughts of gratitude which should be felt. Rather, I'm holding out a hand to say that if you're one of those people feeling sad in the build-up to the festive season and you don't feel that you should because your life isn't that bad ... then, please stop, right there.
Firstly, remove that should word from your vocabulary of self-judgements. Secondly, feeling guilt that your life isn't that bad because, let's face it, there's almost always someone who's worse off ... what good does that actually do - for you, or for them? Thirdly, this isn't me telling you to "buck up", it's me saying: "it happens, be kind to yourself, be understanding, offer yourself some slack, allow the empathy to flow in your direction."
If the reason for your less-than-joy is a one-off, or unexpected, just being kind to yourself may be enough ... or all you can do, for now. But, if it's something that's going to come around year-upon-year, then we should be looking at how to make it easier for you.
Will that mean you deciding to go abroad on a holiday? Will you go solo, or will you join a group sharing a common interest or just a shared desire to get away from all the tinsel and jingle bells? Will you plan something special for yourself? A few days in a period cottage with a real fire where you can curl up reading and eating whatever takes your fancy? Or a top-notch country house hotel, where the service is stunning and the facilities to die for? Or will you stay at home, fill the larder with your favourite treats, mooch around in PJs with fluffy socks and cardigans, watching back-to-back episodes of shows you always wanted to see, or films galore? Will you volunteer to feed the homeless, or visit the elderly living alone, or offer to give a carer a break?
There are so many other options - and none is more right than the others, not even the more worthy ones - unless they are what you need to make the Holidays happier for you. Do whatever it takes - because you are worth it.
And it's only just December, so there's still a little time ...