Why are almost all my prayers answered, even what seems impossible, except for one prayer that I have been asking for for eight years, despite my diligence and variety in supplication, and what is the way to ward off the whispers of Satan and the feeling of despair?

A Muslim must have a good opinion of Allah and not despair of the supplication being answered, for it may be answered as long as he does not hasten and say, "I supplicated but I did not see it answered," as stated in the Hadith. The response is not limited to obtaining what is requested; rather, Allah may store good for the supplicant in the Hereafter, or avert evil from him, as in the Hadith: "There is no Muslim who supplicates with a supplication in which there is no sin or cutting off of kinship ties, except that Allah will give him one of three things: either He will hasten his supplication for him, or He will store it for him in the Hereafter, or He will avert from him an equivalent amount of evil." Therefore, one must continue supplicating with certainty and be content with Allah's decree.