Absolutely true. We learned this from experience. It's good to make your boundaries ahead time and stick to them, lest you be swayed in the moment. Manipulators know how to use your good intentions against you.

You have to say, "this far and no more," and sometimes you have to just say no. But the best protection is to listen to the Lord and follow His voice. Nothing is hidden from His sight, and He give wisdom for the asking.