Christmas cactus may drop blooms if stressed by radical shifts in light or watering regimes, although this isn't a sign that the plant is dying.
Keep plants in a bright room but away from direct sunlight.
As with poinsettias and cyclamen, the blooms will last longer in a room that is kept on the cool side.
In flower, keep the soil moist but not wet -- the pot must drain. After blooming allow the plant to rest by cutting back watering.