Just as colour added to water makes it unclear, so desire for things muddles the mind making it difficult to remember.
Just as it is impossible to see into boiling water, likewise a mind seething with resentment or anger cannot clearly see.
Just as the bottom cannot be seen of a pond covered with, weeds, a sleepy, lazy mind cannot see to understand it clearly.
Just like the surface of water is stirred up by the wind, a restless mind is agitated and cannot think smoothly.
Just as it is impossible to see through water in the dark, nothing can be found in the memory when they are doubts about what has been learned.
These states of mind are the five hindrances (panca nivarana) that obstruct the mind and prevent it from concentration and clear thinking. Strong, energetic, trained control is needed to keep these five hindrances from overtaking and imposing the mind. Meditation frees the mind from these hindrances, gradually and surely; and it awakens the mind to wisdom. An unobstructed mind can think clearly and remember well. When the mind is alert you should be able to do your studies well.