So my Christmas cactus was seemingly healthy...growing new little nodes until today, when two of the bigger sections (growing off one base piece) just up and FELL OFF...I took the base piece out and it was dry and very sick looking (photo attached). But the top pieces were nice and green. I only have one small section left and I really hope it doesn't die off too! Any help with what happened or how to prevent/correct it would be appreciated!

I am no expert but I am growing 4 Christmas/Easter cactuses at this time. One I have had for 3 years. When the same thing happened to mine, I took it out of the pot only to see it was not draining as it should and so it rotted at the base. I have since repotted it in better draining soil and it is doing great with new growth and everything. Seems I caught it just at the right time before the rot killed everything. I am happy since it is a treasured gift from a gardening friend. I moved it from the a/c indoors to the greenhouse where it gets mottled sunlight, more humidity, and heat. I miss my plant inside the house and will probably acclimate it come fall and hope for blooms again. But it seems happier outside in the heat and humidity. I do have trouble with yellowing leaves though.

My newest cuttings I got in March and April have tripled in size. They are in half soil and half perlite and sit next to the above established cactus in the heat and humidity. They all get frequent misting but watered lightly only once a week.

Yours looks like it's probably Schlumbergera truncata. There are quite a few pics in the database here:
Christmas Cactus (Schlumbergera truncata)

You might want to take some cuttings of the good-looking parts, as well as repotting.

The info here is excellent:
http://www.clemson.edu/extensi...

Thanks for the page, @purpleinopp I think I will move mine into more shade. That won't be a problem. there is plenty of it here! The problem will be finding it longer nights come fall. I might have to fool it some how. I have 3 supposedly Christmas/Thanksgiving Cacti. I I am almost sure it Thanksgiving. The other new cuttings may be Christmas because they were still remnants of bloom in late March. However the cuttings did not come from my climate zone. So I will wait and hope for a bloom to look at the antlers to know for sure.

Happy to pass it along. This site is excellent for showing the difference between the 3 types:
http://archive.is/75Nv
The shape of the flowers is completely diff on the 3 types.

Bloom time is probably an unreliable measure, away from natural habitat area (latitude.)