Check your local library for audio training on how to speak up and say no to people. Learn how to set healthy boundaries by utilizing available lessons. Even if you get only one useful idea, it might be all you need to completely transform your life and relationships.
You let go of the idea that giving yourself up to others somehow makes them care more about you! It doesn't. People should give in because they want to, not because they feel pressured or that it will be a deal breaker for the friend ship or relationship. If we respect ourselves and say no gracefully there should be no problem, if there is, it's their problem.