You are basically telling god... that you know what is best, more than god does
pray is asking,and if you asking something,did you really know what the best for you?you ask what you want,and sometimes god give you what you need.
people pray for what they want,gods answer with her own way,if god give all you want at the first time you ask,then you will not know how to patience,and you will leave god,so people pray for profing that they believe in god.