Although we are told that all prayers are answered
Although we are told that all prayers are answered, it seems to us that many requests remain unfulfilled. Though tefilos (prayers) are never rejected, this does not mean that Hashem complies with our total request. He may answer it only partially, or sometimes put it aside, for Hashem knows what is best for us.
Rabbi Yehoshua son of Levi said that Tefilah brings about a fifty percent reprieve. (Va’Yikrah Rabbah, 10:5; Devarim 8,1) When Hashem’s anger was aroused against Aharon, he was condemned to lose all four of his children. (Devarim 9,20) Then Moshe davened on behalf of his brother and two of his children were spared. Even though Moshe Rabbeinu was refused entry to Eretz Yisrael, his numerous prayers enabled him to see the land. (Devarim 3, 26-27; 34,10)
The Steipler writes that there are some prayers that are answered immediately, and others that are answered after many years. Ultimately one will see how much his prayers made a difference. It is impossible for a person to know what his present predicament would have been like had he not prayed; without his prayers, things could have been much worse. Our prayers greatly ease our situation.