While I agree that will power is based on your belief of your ability I cannot help but wonder of how effective it is to keep studying without breaks for memory

While I agree that will power is based on your belief of your ability I cannot help but wonder of how effective it is to keep studying without breaks for memory retention and recall. If you read in "Use Your Head" by Tony Buzan there are graphs that show that the longer someone studies for the worse memory retention and recall becomes thus making it totally ineffective and pointless to exert the willpower to keep study for extended periods of time.