Being a Christian heavily involves repenting, turning from your sins, and living a new life. It also involves believing that Jesus died for your sins and rose from the dead, but that is meant to affect you to make him Lord of your life and start striving to obey His commandments. Praying a prayer and saying "I love God" doesn't change anything, much like a man telling his wife he loves her every night and yet still living the way he wants to, regardless of her. The book of James says that belief is not enough; even the demons believe, but that doesn't make them Christians, because they hate God. Your belief has to change you somehow; you have to submit yourself to Jesus to truly be a follower of Him.