Just got back from the test centre... Bombed it. 580 (q37 v33). I've been preparing for this damn thing now for 18 months... I don't konw what I'm doing wrong... I know I'm not stupid

btw my last GMATPrep was 640 (q42 v33) which I took one week ago in the local library but a person kept coughing behind me and I couldn't concentrate during verbal, my verbal is normally at v40-42 and my last 2 quants before that were q44.
I think I know why I bombed it:
* I'm really burnt out and exhausted from it all at the moment. In the past 2 weeks I've done zero prep, I just didn't have it in me.
* had a very early start - the exam was at 845am, 1 hour from my home. I'm not a morning person.
* Not much sleep last night.
* Became very tired during verbal and couldn't concentrate at all in the 2nd half of it.
* I just wasn't ready, and I knew it. I should have listened to my intuition more...
Anyways I am off back home to Australia tomorrow for a 2.5 week holiday, I may just do 1 hour a day max on weak areas whilst I'm away and then get back into it again when I get back... when I get back though I only have 4 weeks until R2 deadlines... Should I just postpone applying until next year? or am I close to that 700 (with a quant of 47-50 ideally), but just had a bad day?
I really don't know what to do at this stage to improve and get "back on the GMAT horse".. I've used most of the
MGMAT CAT's and have done most of OG12... Any advice?