I should have known

I have never been the kind of person who thinks I should be married to my job. I do have a good career and want to further my career but not at the expense of my life and family.They have always been first and work second. I changed from working the day shift to the night shift because of my health. I am a diabetic as many of you know and it is just much easier to control my blood sugars working the night shift because it is not as fast paced as the day shift. I can take my medicine and eat meals at regular intervals. I talked to my boss about this and she agreed that I should do whatever I needed to to be healthy. Next my son and his family are coming in for one weekend next month; I requested it off. I put in the paperwork needed. I am working on Friday. This is bad because they come in early Friday spend the Friday and Saturday and then leave early Sunday morning. SO working Friday night takes literally both days away from me. When I saw this along with the fact that a day shift had been thrown in there I was soo mad I could not talk. I must have looked the part to because several people asked me if I was ok; I told them I was just upset about the schedule and could not say anything more. I actually had a lump in my throat when talking to them.
My biggest prolem is I have been a nurse for 14 years. I have paid my dues with working flip flop days/nights in the same week schedules. I have worked every holiday, I have worked the crappy schedules. I think I should be able to claim something for that siniorty! Most of the floor are new nurses who have been nurses for less that 1-2 years and they cry and complain when they do not get their way so they get their way! I am sorry it is not FAIR!!!! I do not cry and complain I usually go with the flow and do what needs to be done but this time I am just mad about it!
I am sorry this is not my usual chipper self posting. I am upset and need to vent and this is my forum. I am going to send a email to my boss and the schedule maker and let them know I can only work one shift and since night sshift is working for my health that is the shift I want to work and since there are openings on that shift I do not see a problem with this since I talked to my boss about it before and she agreed. If I need to get a doctors excuse stating this I am sure I can.
Thank you for letting me vent my frustration.