Everybody's different, but for me, if missing this run helped to prevent me from hating running, then the psychological benefit of missing it outweighs the physiological benefits of doing it. Does this make sense?
With increases in mileage and training, you eventually reach a breaking point where the added work simply makes you hate running. This just happened to a good buddy of mine who was training to make the Oly trials and just finished top 100 in Chicago a week ago. He's fit from 2 years of making himself crazy with training, but now he wants to quit because he's so damn sick of the sacrifices. I told him, focus on shorter distnaces for a while, and train less. You've gotta love the sport if you're going to do well.