I am delighted to hear that you are thinking of what is best for you first. You are taking your power back! After a history of putting others first, I have discovered that this does not earn us what we think it should. Typically, people take advantage of our good nature without regard and we become the proverbial doormat.
I have noticed that when we do stand up for ourselves and take our power back, it can be very baffling to those who have taken advantage of our nature forever. It may be wise to have that dialogue with your mother that Gail suggests. Kindly tell her that you feel as you do (a doormat or however you choose to state it) and that you have decided to speak up when things do not work for you and have chosen to put yourself and your schedule first and foremost. It is obvious that you do love and care for your mother very much and don’t be afraid to let her know that but it is time for you to listen to yourself and stand your ground. I have often felt that it is not what you say but how you say it that makes the difference. One of my latest affirmations prior to discussing a "situation" with another is: "I listen with love, I respond with love"...
I also think the key is in listening to your inner voice and following its direction – that is, I believe, your spirit talking. When we are not in touch with our own spirit, we are traveling in a direction contrary to what is in our best interest. I remember clearly one night when I was tidying up my entry a voice said to me, “you had better put that mat outside on the entry step”. Of course I did not listen and the next day, coming home with coffee, I slipped and sprained my ankle right where I had thought to put that mat the night before. That was a very painful wake-up call! I think most everyone has a story similar to tell. Anyhow, I have recovered from the sprained ankle incident but know that I have to be careful – stairs can be treacherous. I will never ignore that little voice again!
So, dearheart, take a deep breath and when making a decision, do not feel too hasty or pressured to make a commitment that is not right for you. If you do, take the steps to correct the situation asap. Always, be true to you!