Easygoing people still have a line. Chill isn’t the same as limitless.

Being relaxed about most things gets read as having no limits at all, usually because the limits never came up. Then the one time you say no, people are startled, as if you changed character. Chill is a preference about small stuff, not a standing offer on everything. Having a line is not a contradiction of being easy to get along with.

Say the small no out loud more often, before you reach the big one. Not as a correction, just so your limits are part of the normal picture. People adjust much better to a line they have seen before.