Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you: For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened. - Matthew 7:7-8
And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you. - Matthew 17:20
I'll be the first to admit that I've struggled with these verses. You see, I have asked for things in faith, but God chose not to give me what I asked for. Why? I'm not sure, but I know He had a reason. So, is God a liar? Is the Bible inconsistent? No, not at all.
While the Bible does point out the importance of having faith, it also tells us that God does not always give us what we want. Look at these verses for example:
Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts. - James 4:3
And lest I should be exalted above measure through the abundance of the revelations, there was given to me a thorn in the flesh, the messenger of Satan to buffet me, lest I should be exalted above measure. For this thing I besought the Lord thrice, that it might depart from me. And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me. Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ's sake: for when I am weak, then am I strong. - II Corinthians 12:7-10
It's so easy to pick and choose a couple of verses and then claim we know what the Bible says about a certain topic, but we must be very careful. Sometimes we know just enough of the Scriptures to get ourselves into trouble. That's why it's so important to know God's Word inside and out and to compare Scripture with Scripture.
Just to make sure we're all clear on this, I believe that God wants us to live our lives in faith and that He will reward us for that faith. I also believe that God can do anything. Whether He will do something or not is completely up to Him. He is in control, and I have faith that He will do what is best. God will provide for me in His way and in His time. I can't ask for any more than that!