I also feel it usually takes 4 or 5 races to hit your best marathon for your body to be accustomed to the training AND the race itself.
One wakes up one year and realizes you did not produce as good a set of races as the year before.
You aim to win the same races you won before, but your time is done; there is someone who is hungry, really hungry.
Lastly, races bring a lot of energy into your focus on running, and are (usually) a good time.