The abilities Vital Spirit and Insomnia prevent pokemon from falling asleep. The ability Early Bird helps you wake up sooner than you otherwise would. Aside from that, give your pokemon chesto or lum berries.
Also, remember that if you already have a status you cannot fall asleep, although I don't see how that will help you muchas you won't be self inflicting in all liklihood and another status will hurt you anyways... Still, it could be better than having darkrai eat your dreams and give you nightmares.