Just say no?

I think I've mentioned previously that I'm leading a Bible Study called "The Frazzled Female: Finding Peace in the Midst of Daily Life". This week's study is entitled "I Don't Have Enough Time" and is all about time management and making God a priority and eliminating unnecessary resposibilities so that everything else falls into place. I'm really struggling with this and feel woefully inadequate to be a leader on this topic.
It's not that I don't strive to make God a priority in my life - I do. I don't always succeed, but it is one of my goals. But about the whole "eliminating unnecessary responsibilities" thing: exactly which of my responsibilities are unnecessary? Should I give up speech therapy? Maybe teaching my son to eat is optional? No, I know - laundry & dishes. I would love to give up housework! (Who am I kidding - my husband does more than his share already!) Perhaps I should eliminate some of the specialists' appointments. Pulmo? ENT? Optho? Who needs 'em!
Obviously the things that are overwhelming to me right now are not unnecessary responsibilities. Does that mean there's no hope for me to "find peace in the midst of daily life"? I sure hope not! I guess maybe it's just a little bit harder when the solution is not just saying no to bring that extra casserole to the church dinner or serving on one less committee.
Sometimes I wish my life were that easy, but then I realize that I would miss out on all the good things. Like the little boy running around my living room with a strainer on his head saying he's a "fider fider" (fire fighter) and pretending to put out the Pampers' box that's apparently on fire, for instance. I'd better go help!