Body Tells Me to Skip Today's Marathon Race

Today was going to be my return attempt at a marathon race, but during the last two days I suffered from a great amount of insomnia...and sleep deprivation is not an advisable preparation for running 26.2 miles.  So instead of arising at 5 this morning...with hardly any sleep...I decided to chill out and skip the event, precipitating a good, healthy night's sleep.  I'm disappointed that, although I seemed to be preparing for the race the way others advise, my own body ended up casting the crucial dissenting vote for participating in it.  I do like running, but at this stage in my life I think that half-marathons are probably going to be the maximum distance I'll be doing...