Just moving a poinsettia from one place to another is enough to cause mayhem. They can't take cold drafts. Even the car ride home and those 10 fateful steps from the car to the house is shocking and can cause leaf drop, then the dry heated home just hastens the inevitable. You didn't do anything wrong. Poinsettias are poor candidates for houseplants and are typically sold here as 'holiday ornaments' and promptly discarded afterwards. I certainly wouldn't give one as a gift. They can be toxic to pets.

Alocasias, Hoyas, Peperomias, African Violets, Schlumberger, Aloe, Crassula, Monstera, Spider Plant - all excellent houseplants.

I suspect it is just the change in temperature. if it has come from a supermarket then your home will be warmer and probably drier. Bathgate is correct the cold from shop to home will do for them, this problem exists for the the large flowered cyclamen.
if you do get another one leave it in its plastic sleeve for a day or too to 'cushion' the leaves against the air changes. then make sure it doesn't get drafts and it isn't on a shelf/window sill above a radiator as that is certainly going to cause leaf drop. My mum always lost hers until I saw where it was [window sill above radiator next to a door]. they prefer strong bright light too.

There's an old, long thread on here somewhere regarding Poinsettia at Christmas. My experience of these is they nearly always look dreadful fairly quickly, starting with dropping leaves which often go black first, so they're defoliated within a week or two. In all the years I've bought them, I've had 3 which still looked good weeks later - all the others didn't, and given I've been buying them for 30 years or so, well... It doesn't seem to make much difference where you buy them either - one Marks and Spencer one looked awful within a week, but another from there the following year did really well. The other two that did well came variously from Tesco and Waitrose. These days, I leave it till the last possible moment to buy one in hopes it'll at least look fine for Christmas Day and Boxing Day... I remember when Tesco had a 'promise' on these - if it didn't last two weeks, you could exchange it,and one year, I took back two for exchange - it didn't last long, they only ran that for a couple of years!

If you've not over watered,its not in a draught and not near a heat source, its not your fault, is what I'm trying to say - its more to do with being hot house mass produced, transported, and transported again after you've bought one, so essentially, transition shock. Probably a lot safer to buy a Christmas Cherry (also called Jerusalem Cherry, Solanum capsicastrum) for Christmas decoration purposes, though these days, they are much harder to find.

Thanks as usual! I know these plants don't last that long and are usually given as gifts just before Christmas to be typically discarded after the festive season. They look very nice in M&S in a crowd and I have always wondered if shops spray them with something to keep them looking fresh. However, the one I have now has broken all comers records and started to shed leaves almost immediately. I was, however, given one at work some years ago and it lived on and on. It never looked good and only ever developed one or two red leaves around this time of the year. I never throw away a living plant, no matter how sad it looks but it does go to show an exception to the rule. Thanks also for your suggestions for alternative indoor plants.

My family have all been warned not to buy me any poinsettias as I spend too much energy trying and failing to keep them going. I hate just watching plants die!

So do I, Pennyfarthin! I always feel guilty even when people convince me it is not my fault, like the other contributors here.

I live in a sunny part of Australia - the Gold Coast - and mine grows like crazy outside. It's all about the climate matching the origin of the plant as much as possible. This plant needs lots of sunlight and likes to be watered, but not soaking in water. Warm enough to be comfortable for you.
The northern hemisphere is just not compatible enough at Christmas time. I think it's all in the forced conditions to market this as 'Christmassy'. Don't worry about it. There's heaps more beautiful plants out there.

Thanks, Jenniferjun! Are you trying to make me envious telling me that you live on the Gold Coast, which must have been one of the places I have seen them growing naturally!!! You have succeeded! I have a relative in Melbourne, Phillip Island at the moment, and she grows a lemon tree. She said she got 40 lemons off it. I tried this and it was a disaster! Season's Greeting to you!