"Mat 21:22 If you believe, you will receive whatever you ask for in prayer."
We are in a relationship with our God, who is real and alive, and whom we can know and who knows us, I am a father and when my son asks me to do something or give him something, if it is good for him I will do so, sometimes even if it's not - such as a pkt of chips or a few lollies etc.
I give to my son because I love him and I want what is good for him, and I am in a real relationship with him, we too are in a real relationship with our heavenly father, we do not just get strengthened through praying, we also get strengthened through recieving what we asked for.
Can you imagine how disheartened my son would be every time he asked me for something i ignored him? Our heavenly father is the same, he gives to us what we ask, because he knows what we need and in the process this recieving helps us grow in our faith and in our relationship with him.