Mandatory overtime

So tell me do you think that hospitals should be able to make nurses do mandatory overtime all the time?
I mean I could understand occasionally.   You know to cover vacations or sickness.  I don’t think any employer should have the rights to make anyone work overtime.  It cuts into my time with my family so I don’t sign up for extra shifts.  Not everyone is for the almighty buck.  Some of us realize that family is top priority.  It’s cheaper to pay a PRN nurse than to make us work overtime at time and half.  But they don’t want all the nurses going PRN so they limit how many hours a week that they can work.  20 hours.  Which means they have no flexibility to work if you need them in a pinch.
Here is my problem.  I cut my time back in order to keep my shoulder and neck not to act up.  I was out for almost 2 months the last time it flared up.  So the neurologist told me to stop working overtime and just work 40 hours.  Less stress on my injury.  I will be suffering with this for the rest of my life.  If I don’t take of it now I will cause further damage.  So my manager agreed.  A year goes by and now she wants me re-evaluated.  Even though in the beginning she knew this would be life long.  However someone on days shift is bitching that it’s not fair that my hours are shorter.  Hello…I would love the extra money.  My check is about 150 dollars less….but despite that I don’t want to damage my shoulder any further.  I really would like to choke the bitch on dayshift.  She has no idea the pain I can get in. No idea.  She sounds like a petty grade schooler.  She doesn’t realize that I have to have 5-6 injections in my shoulder to “calm” the muscle down just so I can “deal” with the pain.  So I have to go to my neurologist to get this note to allow me to keep my short week (40hours).  It’s not like I am asking to work less than full time.  So what’s the big deal?  I am pissed enough that I might just post my note on the outside of my locker.