A useful boundary can make the next invitation easier to answer honestly.

A boundary is often imagined as a wall, when in practice it works more like a known shape. Once people understand what you do and do not take on, the invitations that arrive tend to fit, and you stop inventing a reason each time. Vagueness is what makes refusals awkward, because without a stated limit every no looks personal. Clarity is easier on everybody, the person asking included.

Say one limit out loud this week, plainly and without apology. Then hold it once, so the next invitation can be answered honestly rather than negotiated.