I have had a fairly significant disease, but do everything humanly possible to make sure I stay as well as possible so I don't miss work. As my immune system is shot down due to my meds, I do take things such as high doses of zinc and vitamin D to try to help fight against getting sick. I also am constantly sanitizing my hands.
My job is a desk job that allows flexibility. I can use the bathroom whenever I need to, for however long I need to. I can go to doctor appointments I need in the morning/after work and leave early or come in late and make up hours missed. I have the mutual respect thing between my boss and I, showing her that I am trying my hardest and stay true to my word in making up time missed. I always warn that things can go south quickly, and alert my boss if I feel like it is getting to that point, but I do everything humanly possible to not allow that to happen.
Overall, I try to keep as stress free as possible... try not to worry about things too much and just concentrate on my work. It has helped thus far. I feel lucky to be where I am. If you feel you can't work, or it is too hard though... then try to get disability. I know everyone's disease is different, and everyone handles it differently. It is just so unique to the person.