No, you may not be fired for having a bad day living with MS. The Americans with disabilities act was created for people living like us. Check out why that is. Look it up on google.

Employers are not exempt from the ADA no matter what their size.

"At will employment" is the proper term

http://blog.gettinghired.com/Home/tabid/159/ent...
If anyone feels they are discriminated against for disability, it is important to act immediately filing any complaints without delay. Right to work has to do with union organization, not having anything to do with firing without giving any reason. I've had that discussion with my husband who refused to believe me. The title "right to work" is deceiving. Off the top of my head I can't think of the proper term for firing without explanation.

I think you'll find this interesting @A MyMSTeam Member. I'll post the site address.
Right to work states such as Arizona and Georgia, must still adhere to the federal Civil Rights Amendment and ADA law under the enforcement of the Attorney General. Specifically, employers in these states are prohibited from failing or refusing to hire or to discharge any individual or from otherwise discriminating against any individual with respect to the individual’s compensation, terms, condition or privileges of employment because of the individual’s race, color, religion, sex, age, disability status or national origin.