Physical and mental diseases together (secondary progressive MS)

My wife has SPMS (secondary progressive MS) and it has started affecting her cognitive capacity. I can "cope" with her physical disabilities (she is totally dependent for her daily needs), but have no capacity (read patience) with her cognitive problems. She is neither here nor there. She understands all, but short term memory is getting worse, lives by the clock and by very fixed routine. Does not admit to being forgetful, not hearing well, not seeing well, and yet looks well speaks well and I am a sort of a prisoner as she is also a good blackmailer making me feel guilty for going out any errand. She is in that in-between state which is so hard for me to handle. Taking her out is difficult but whilst she enjoys an outing the return home is always to the routine. Why do I bother is a question I ask myself. Obviously because after 46 years (of which 42 with MS) she is part of me and who I am and I just feel that I have to do and want to do all I can for her to feel better. But it's very hard. I have helpers to assist with her getting up, bathed, dressed and prepared to lead a "normal" life. How is it possible not to feel bed when I get angry at her repetitive questions and statements. She is not one to go to a day centre or have "activities" (never was, even when not cognitively affected). I am being selfish I suppose wanting her back and not being able to, and not wanting this continuous living in limbo, as I am neither here nor there in a different sense. I suppose this is what the "for better or for worse and in sickness and in health until death do us part" is all about. I shall, I will and I do. Thanks for reading my discharge. Good luck to us all who are going through this. My wife just fears that I will "go" first. But we always finish the day with a smile and a kiss. Will it be better tomorrow?