Behavioral boundaries are the most effective long-term tool for managing difficult people. Unlike emotional reactions, a boundary is a statement about what you will do, not a demand about what they should do.

This works for quiet behavior too. With a chronic interrupter, compare "Let me finish!" (a demand that invites pushback) versus "I'll share my full point, then I want to hear yours" (a boundary you control). With scope creep, swap "Stop adding tasks" for "I can take this on once we drop or reschedule something else." Because you have already decided your response, the other person loses the power to derail you.