Pruning a Ceiling-Hitting Euphorbia trigona

A 20-year-old Euphorbia trigona has reached 7 feet and bent against the ceiling. Prune it back boldly: use a sterilized knife to cut the tallest arm(s) down to a desirable height, cutting at a joint if possible. Wear gloves—sap causes rashes. New arms will sprout near the cuts, creating a bushier plant. Kew Gardens doesn't need it; your living room does.

This is routine maintenance for a thriving succulent. The plant will recover vigorously.