If you are in receipt of flying pay then try to hang the discharge out until the 12 month from downgrading point, this is the point you will lose it.
It is traumatic to be MD'd at short notice, but however traumatised you feel make sure you:
Get a full unedited copy of your medical notes.
If you disagree with the assessment of your illness/disability that you challenge this withing 6 months of discharge, anytime after this and you cannot challenge the attributable percentage which has far reaching tax implications for the rest of your life. RBL/PS can advise further.
Always always appeal your level of disability and also bring in any other pertinent ailments and injuries. Your level of war pension (yes I know the term has now changed, as have the criteria) relies on this.
Above all do not let them shaft you, even if you have not been in the rank for two years you are still entitled to that ranks pension, remember it's THEM kicking YOU out, not vice versa.
Good luck.
TBT