I was asked by a fellow for advise on what he could do to support his partner as she was going through a rough patch. I told him this:
Love her. Let her know how much that you love her, that your love is unconditional and that you will take care of her when she is needing care just as she takes care of you. Our biggest fear is that we will end up alone, unwanted and unloved, useless and worthless. Let her know that you will move heaven and earth for that to never happen to her. Encourage her. Let her know how much you appreciate the things that she does, especially those things that she must struggle to do today that were easy to do yesterday. Allow her to mourn the loss of the self and life that was before she got sick. Because of the relapsing-remitting nature of M.E. the losses never stop and the grief never does either. Celebrate the good times, the good days. Those are precious and often rare. Court her. Be her prince each and every day, even more when she is feeling more like a frog than a princess herself.
Supporting a loved one going through a tough patch can be a difficult and frustrating thing. People often have no idea what they can do to make better a situation that they have no control over. They give up and turn away just when their loved ones need their help and support the most.
People write long articles giving advice, mostly useless. I won't do that here. That nutshell of advice is perfect as it is.