One thing I am doing, and not apologizing for, is saying no. I recently was faced with a circumstance of putting this advice into action. I received an invitation and I did not have an actual conflict. However, I still declined. This person is not a close friend of mine although I hear the grapevine she was "surprised" that I did not attend -- read: probably pissed. And you know what, that's ok. I have to let go of putting other people's needs before my own...now, more than ever.
I came across this really worthwhile article by Kris Carr on the very same topic. It's worth a read. And I appreciated one commenter's view: "don't think of it as saying 'no' to someone, but saying 'yes' to yourself."
Mindlessly agreeing may temporarily avoid discomfort, but it’s often short-sighted and even lazy. Instead of setting a boundary, we slip into “yes” amnesia, forgetting we’ve been here before. In this delusional state, there’s unlimited time, superhuman energy and a gaggle of soul-nannies who keep us fed, bathed and exercised. Sober up! Splash yourself with cold water and (gently) slap your cheek. If you’re worried about scarcity, let that go. Offers and opportunities will continue. Every unwanted “yes” takes you one step further from freedom, well-being and time with yourself and loved ones."