Marathon training

Well as any of you know me you know i have been training to do a full marathon in October. Now i have completed many a half marathons and have slowly improved, i have done two halfs and a fun run so far this year.
well today my training had me run my furthest distance yet.. 32 km.. i have to say mentally i was totally prepared and did okay with it but physically it was very very challenging. so now i am left with the question of do i really want to do this marathon. will i be ready to do it in a little over a month. i am so disappointed right now that my body is so tired.  I will have to think long and hard over the next couple of weeks.