To make sure your cactus blooms well, fertilize monthly from June through August with a balanced houseplant fertilizer at half-strength.
You can take it outdoors during the summer, too, but bring it back in before it gets too cold.
For about six weeks prior to blooming, the holiday cactus requires between 12-14 hours of dark to set buds.
That means cool temperatures around 50-65 degrees, and no light (not even artificial).
You may consider covering it during the day to ensure it will flower or moving it to the guest room where it won't be exposed to nighttime lights.
Generally, Christmas cacti require less water during fall and winter and more in spring and summer.