First off, major victory there! You said no! Pat yourself on the back!
Yes, it does get easier. I say no to things without even thinking about it now. I also don't care if I offend someone now; "being nice" is what kept me fat after all. I've refused snacks and dinners from well-meaning people, but if I'm not hungry and/or don't know how it was prepared then sorry I don't eat it. If that "offends" someone, then so be it.
I've said this before but, nobody can force you to eat something you don't want, be a b*tch if you have to.