Saying No

Why do I have so much trouble saying no? I feel quite overwhelmed with what is put on my plate right now - caring for 3 kids under the age of 8, homeschooling, getting kids to their activities and practicing for them, taking care of the house, meal preparation, teaching dance and prep and extra time that that requires, competition coming up, which means several trips in to the city, church, friends..... Then when someone asks me to take on more or help out, I feel like I should and when I don't I feel guilty. These people don't make me feel guilty, I do. I love helping people. And usually it gives me more energy helping out. But on those occasions I feel I can't - I get disappointed in myself. Why do I think I can be all things to all people? Why do I have very little grace for myself? When others say 'no' to me, I don't have a problem with it, so why do I not let myself say no.
Recently, I have been asked last minute to come help some girls get ready for their Ballet exam. I have been helping by taking their lesson once a week, but the teacher that was doing the majority of the training for the exam just passed away. I felt like I should have jumped in and taken the last couple lessons but I didn't know how. I can't let my boys just be there while I taught - that would be mayhem (As I type this there is howling in the background), I don't have childcare, as my family is in B.C. and my friends can only help so much, what with their busy lives, and ultimately my first priorities are caring for my family and getting school done. That seems enough - but then I have so much more to squeeze in. Sometimes lately I just zone out thinking of summer, and less commitments. I just crave that. I just want to sit in the sun, dig in the dirt, think, pray, play....
Even the church, as many that their needs are and as called as I am to being involved in the church as a "spiritual family", becomes a weight sometimes I dread bearing. But what I am wondering is do I serve a Savior or I am I trying to be a Savior? Now there's food for thought!