Don't be intimidated about pruning. Cutting back and thinning the older branches will result in larger blossoms. If you simply deadhead the old blooms or do minimal pruning, you'll get smaller bracts.

The red "flowers" aren't really flowers, they're bracts or specialized leaves that are usually located under the actual flower. When plants have insignificant flowers, they often develop colorful bracts surrounding the flowers, to help attract bees and other pollinators to the hard to find flowers.

Bougainvillea and Kousa Dogwood are 2 other examples of flowers that are actually bracts. Even though the red Poinsettia bracts aren't really flowers, they make a wonderful display.