I need a break!

Lately, my life has been extraordinarily busy. I look at my calendar, and I have something listed every day! Why is it that I have so much trouble saying "NO"? I'm afraid I will seem rude or uncaring. I feel guilty for wanting to spend time at home working on the mountain of laundry in my bedroom, for wanting to spend time with my husband and my children, and especially for wanting to do something just for me. I feel like people have these expectations of me, and when they aren't met, I am worthless in their eyes.
As a teacher, I am expected to be everything for every student. During the course of one work day, I am a parent, a counselor, a nurse, a disciplinarian, a cheerleader, a career advisor, a maid, a secretary, a child advocate, and an educator. If I drop the ball on one of these, I might as well have failed at all of them. Right?
As a pastor's wife, I'm expected to...Well I found the following passage about pastor's wives online, and I can't put it in better words...

"We are called to be all things to all people at all times in order that we might win some. Our attitude must never be guided by our emotions, a slight, a rejection, a burden or a criticism. We are to hold our heads high and smile at all times. We must shake every hand and pat every head and hear every complaint. We must always know where our husbands are, and be ever-ready to relay any message to him, and if he doesn’t act upon that message, we are accountable for his inaction.
Our children must sit in absolute silence while listening attentively to every word our husbands say. They must be dressed in spic and span condition and exemplify all the fruit of the Spirit. We are to have a perfectly clean and organized house. We are to live on less than what our members live on but dress above our means and bring elaborate dishes to every potluck.
We must be in attendance at everything at all times to support the work of others in the Lord. We are to answer questions of “What do you think?” with non-answers that have nothing to do with what we think, but with neutrality. We are on call at any moment, at all hours of the night, to carry on without our spouses and we are to get absolutely giddy for the pleasure of not having his company. We are not to be sick or in need of our spouse’s attention. Our opinions and thoughts are not our own, but representative of our husband’s. And he is held accountable for all we think, say and do."

I think the above passage gives a pretty good list of reasons why I feel like I can't say NO. Are all of these things true? Probably not. Are these really the expectations that others have of me? I really don't think so, but at the same time, these are the things that gnaw at me when I can't be Superwoman.
These are the moments when it is important to remember that the only One I have to answer to is God. God set me apart to be so many things in my life: daughter, sister, wife, mother, pastor's wife, teacher, friend. But the greatest role I have ever had is a child. His child. What others counted (and may still count) as worthless, God counted as significant. He has a plan for me. He lives in me and I in Him. He will never let me go. He will take my burden and give me rest. And that's all I need.