What is the remedy for my problem of forgetfulness and excessive fantasizing, which have negatively affected my academic performance and religiosity?

This worldly life is fleeting, and the wise person is he who takes from it provisions for the Hereafter, while the loser is he who is deceived by it and by delusion. The capital of a human being is his religion, and its loss means the loss of everything, as Allah Almighty says: (Say, "Indeed, the losers are those who will lose themselves and their families on the Day of Resurrection. Unquestionably, that is the obvious loss.") You are in a battle with Satan, so do not surrender to his whispers. Strive against your soul to follow the path of guidance and success: (And those who strive for Us – We will surely guide them to Our ways. And indeed, Allah is with the doers of good.) Elevate yourself towards noble aspirations, and beware of procrastination. Piety is a gateway to knowledge and guidance, for whoever fears Allah, He will grant him a criterion, atone for his evil deeds, and forgive him. Identify the causes that weakened you and try to get rid of them. Raise your hands to your Generous Lord, for He is ashamed to return them empty and disappointed.