Hadith.1445 - A Bedouin came to the Prophet (sw) and said:
"O’ Messenger of Allah (sw), I used to have a strong memory but now I have become forgetful."
The Prophet (sw) asked: "Did you use to take a midday nap (Qailulah)?"
The man replied: "Yes."
The Prophet (sw) then asked: "And did you stop doing that?"
The man answered, "Yes."
The Prophet (sw) said: "Resume it."
The man did so and his memory returned.