The person who accepts your limit has made the relationship easier to keep.

A limit that is met without argument does something quiet and large. It removes the cost of having needs in that relationship, and once that cost is gone you stop rationing contact, stop rehearsing conversations, and stop avoiding the person on the days you have nothing spare. Acceptance is not the same as agreement, and it does not require them to understand.

Notice who does this for you and say so, because it usually goes unmentioned. Then look at where you are the one asking for a defence. Letting a limit stand without discussion is a small thing to give.