Being a good person doesn’t mean being a doormat with good manners.

Being decent and being endlessly available are different things that get bundled together constantly. Kindness with no limits stops working as kindness and turns into something other people organise around, usually without any malice and always at your expense. Saying no is not a failure of character. It is what keeps the yes worth anything.

Find one place where you have been agreeing out of habit and decline once, without a long justification attached. Notice that the relationship survives it. Good manners and clear limits fit together more easily than you would think.