Evening before my First Half Marathon,or not ?

If everything goes well then I should start in roughly 16 Hours my first Half Marathon , problem tonight is that I'm not feeling too well, the cause could be either a upcoming Cold in that Case I might not be able to do this tomorrow or the other Reason could just be that my Body is somehow rebelling.
 I think there is a small chance that I'm getting slowly into the Menopause, that could explain the on and off Feeling I sometimes have.
So I hope I can start the Race tomorrow, I have not even remotely enough trained but I think this Race will be a closure of the current Season and then I''m really looking forward to what  I call next Season the Start of my Triathlon Season