Sometimes you just can't sleep no matter how tired you feel. If it's just a odd occasion that pops up I wouldn't worry about it to much. Just lay up in bed or on the couch and flip the TV on, something boring is bound come on and send you to sleep. And hey right about my time here Jay Leno and David Letterman is starting, that's guarantee to put me to sleep if I watch it for more then 5 minutes!