So lets flesh this out a little more. Sometimes we want to know God's purpose because of our pride and greed - "Jesus loves you but I'm his favorite". But that might be painting with with a really broad brush. Lots of people read Rick Warren, not all of them are so egocentric.
I think some are searching for God's purpose because they really want to know. But they are searching for God's will in the wrong place. It's almost like going to see a palm reader, or a tarot card reader, or checking your horoscope. From time to time people contemplate major life changes: school, marriage, job, children, location, etc. These are big things. They are intimidating things. People want to know if they make the change and go back to school, change jobs, get married will God still bless them.
Of course He will. But not because you finally found "His will for your life". God does have a will. Here it is: obey the commandments (love God, love your neighbor), and die to yourself and be saved for the sake of Jesus.
But we freak out. Stuff doesn't always go the right way. Sometimes people make a change and get stressed out, loose money, get too busy, depressed, whatever. We really want to avoid those bad things. We think that if we can tap in to God's master plan we can avoid that stuff. Good luck. It's a sinful world. Bad stuff happens. But that doesn't get in the way of God's will.
Read Ephesians 1. God loves you. He chose you from the beginning of the world. He sent his Son to die in your place on the cross for your sin. You will go to heaven. That's God's plan for your life. That's God's will. We spend so much time worrying about His plan and purpose in this life that we make it way more complicated that it needs to be. Read the Commandments. Confess your sin. Believe in the God/Man hanging on the cross for you and be saved.