1. Your benefit (for what you have asked could be a harm to you in a way)
2. Your sins (for the sinner's prayers are not answered).
If it was the second reason, you will have to clear the path of answering from the stains of sins.
If it was the first reason then look at what you ask for..is it to strengthen your religion, or just a plain earthly desire?
~ If it was only an earthly desire, then know that it is the kindness and the mercy of Allah that delayed it for you, and by your insistence, you are like a child that asks for what harms him and he is denied that for his own good.
~ And if you think that what you asked for is for the benefit of your religion then your benefit could be in delaying it, or the well-being of your faith is by the nonexistence of it.
In other words, the planning of the Truth the Almighty (Allah) is better for you than your own planning, and He could deprive you from what you ask to test your patience.
So let Him see from you a determined patience and you will soon see from Him what will give you joy.
And when you have cleaned the paths of answering (of supplication) from the stains of sin and was patient about what He has chosen for you, then everything that happens to you is better for you whether you were given or deprived of what you have requested.
[Imaam Ibn al-Jawzee (rh) ]