I am sorry to hear about your wife. It is definitely hard, there is no doubt about that. My Mom was diagnosed around 2010, as well, and she has unfortunately lost all mobility from the waist down. Myself and her boyfriend take care of her, make her dinner, clean, help her shower, and it gets tiring. I deal with my emotions when I am frustrated, by leaving the room for a minute to breathe, and to think about and realize the situation. Most of the time, I think, this isn't about me, so I should and need to settle down. Sometimes I think, do this out of the love of family, because you're her support system, be her strength. No matter what, do it because you love them and you know if it were you with MS, they would be right there for you.
I hope I could help in some way. God bless you and keep on keepin on!