Forgetfulness can arise from stress, depression, lack of sleep or thyroid problems.

Other causes include side effects from certain medicines, an unhealthy diet or not having enough fluids in your body (dehydration). Taking care of these underlying causes may help resolve your memory problems.

Interference due to emotional problems, anxieties, distractions, intense concentration on something else, and intellectual interference

Intellectual interference or mental overcrowding can be minimized if we reflect on our reading and experiences, understand them, clarify them, associate, and organize them so they will not interfere with each other.

We must avoid cramming and overcrowding our learning hours with unorganized material. There is more interference between two similar subjects than between two unlike subjects.

(Follow study of history with chemistry rather than English history or literature.) Furthermore, there should be rest periods at intervals to allow the brain to lie fallow. Continuous undifferentiated activities apparently fight for a place in the memory.

Since we cannot be awake without thinking, it should follow that there is more loss of memory for learned material when one is awake than when one is sleeping. (So study and then sleep.)