I think keeping appropriately fueled and hydrated will make a big difference. Aim for around 200 calories an hour and 12 to 16 oz of water or energy drink and hour even if you're not hungry or thirsty.
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A conclusion is the place where you got tired of thinking. - S. Wright
Favorite rides in the stable: Indy Fab CJ Ti - Colnago MXL - S-Works Roubaix - Habanero Team Issue - Jamis Eclipse carbon/831