This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us. And if we know that he hears us—whatever we ask—we know that we have what we asked of him.
1 John 5:14-15 NIV
I think many times we assume that God knows what we want, we ask one time and let the be the end of it, or we ask things outside His will and become upset when it isn't received. The first measure in obtaining a desire is knowing whether it lines up with the word of God. Then, ask Him to come into your life and show you what His will is for your desire as you ask for it. What we expect may not be what we should be looking for... Most importantly, don't give up. Keep asking until you receive an answer.