Emotions can be indeed directly related to your symptoms. Emotional fluctuations can place your body under stress. You should also know that your emotional threshold will vary day-to-day. If you can learn your threshold problems, try to avoid arguments and emotional situations on days when your threshold is low.
Your family and wife should all know that you might need to be "left alone" during your weakness. I have my alone room or alone time away from my family and they have learned to allow me this time. They know that I need alone time because I do not want to lash out and hurt someone's feelings. It is difficult to always have to apologize for outbursts that are brought on by your low threshold. As you progress in life, the continual apologies will become yet another burden you must bear. It is a good way to lay aside those burdens with some alone time I told my family that I love them too much to hurt their feelings; luckily for me, they understand. If those around you understand what is happening physiologically within you, understanding and forgiveness are easier to come by. Your wife might find understanding within MS info pamphlets. Check with your neurologist or the local MS Society/Association.