Edited: Study Arabic
It is human nature to be forgetful, as the Arab poet said:
“He is only called man (insaan) because of his forgetfulness (nasiyaan), and it is only called the heart (al-qalb) because it changes so rapidly (yataqallib).”
Some of the things that may help to combat forgetfulness and improve our memory are listed below:
1. Keeping away from sin
Keeping away from sin, because the bad effects of sin result in a bad memory and the inability to retain knowledge. The darkness of sin cannot co-exist with the light of knowledge.
The following words were attributed to al-Shaafa'i, may Allaah have mercy on him:
“I complained to [my shaykh] Wakee’ about my bad memory, and he taught me that I should keep away from sin. He said that knowledge of Allaah is light, and the light of Allaah is not given to the sinner.”
2. Frequently remembering Allaah
Frequently remembering Allaah, may He be glorified, by reciting dhikr, tasbeeh (saying ‘Subhan Allaah’), tahmeed (‘Al-hamdu Lillaah’), tahleel (‘Laa ilaaha ill-Allaah’) and takbeer (‘Allaahu akbar’), etc.
Allaah says (interpretation of the meaning): “..And remember your Lord when you forget…” [Quran al-Kahf 18:24]
It has been tested that the action of reciting 'Yaa Qawiyyu' 11 times after 'Fardh Salaah' is a means of strengthening one's memory.
Just as it is permissible to recite other Wazifas for other physical and spiritual benefits, so too is the recitation of 'Yaa Qawiyyu'. However, one should not regard the practise as Sunnah or else it will be innovation (Bid'ah) [Ref: shariahboard.com and Mufti Ebrahim Desai ]
3. Establishing daily Prayers
Be punctual in your daily 'Salaah' and stay in the company of the pious.
4. Not eating too much
Not eating too much, because eating too much makes one sleep too much and become lazy, and it dulls the senses, besides exposing one to the risk of physical diseases. Most of the diseases which we see result from food and drink.
5. Eat healthy and nutritional foods
Eat healthy and nutritional foods that are effective in strengthening one’s memory. Some of the scholars have mentioned certain foods which increase the memory, such as drinking honey and eating raisins and chewing certain kinds of gum resin.
Imaam al-Zuhri said: “You should eat honey because it is good for the memory.”
He also said: “Whoever wants to memorize hadeeth should eat raisins.” (From al-Jaami’ by al-Khateeb, 2/394)
Another thing that can help the memory and reduce forgetfulness is cupping (hijaamah) of the head, as is well known from experience. (For more information see Al-Tibb al-Nabawi by Ibn al-Qayyim).
And Allaah knows best.