Well, I will agree, it is not the MS that can drive a partner away, it is more likely the depression. I came that close to leaving my husband, just to preserve my own sanity....but I am pretty determined to never leave anyone, but that doesn't make staying easier.
A few things he did to improve himself:
He got some Cognitive Behavioral Therapy (at a cut rate price as we were both not earning)
He moved to a place he felt comfortable.
He saw the doctor once he was there and started Prozac...and I think that did help.
He started listening to some Paul McKenna hypnotism dvds, which sort of helped him to fall asleep at night.
He started to do something structured, whether it be cleaning the house or taking a course.
He finally got back to doing his old work in a new position (which was not an easy place to work!!).
It was not easy!! It took a year almost to turn around, and I am so glad it is over.....
Now he is at another new place of work which he loves and is himself again. I really feel it was a physical symptom of his MS...plaques on the brain, that caused this depression, and the inability to handle stress.
If you are still fit, you should definitely take up yoga...try not to lose your core....
There's no point in saying snap out of it, because if you are depressed you just think nothing's possible...but do try to do the above.