People need to hear when an old arrangement stops working for you.

Arrangements outlive the conditions that made them, and the person carrying the weight usually says nothing for a long time. The Sunday visit, the standing lift, the job you always cover: each was fine once and became heavy quietly, so the other person has no idea anything changed. When the break finally comes it looks sudden to them and long overdue to you.

Say it early, plainly and once, before resentment has done the editing for you. Describe what has changed on your side rather than what they have done wrong. Offer the version you can still manage, since most people would rather adjust than lose the thing entirely.