It is okay to be mad or saddened by this setback, but this is just a setback and not an ending to your story.
You can recover from this and there are many here rooting for you. Set smaller goals for yoursel and celebrate those victories.
I found this interesting article on the treatment of GBS. Many of the patients described had good success with multiple rounds of IVIG, sometimes in combination with plasma pheresis. It may be worthwhile discussing it with your doctor.
53 yo female, dx 9/08, AA/hypo-MDS, subclinical PNH, ATG/CsA 12/08, partial response. small trisomy 6 clone, low-dose cyclosporine dependent