By making Jesus Lord, you are allowing the Holy Spirit to remake your spirit, put your sinful nature to death and transform your life. This can only happen when you are willing to give up ALL sin. When even a little of your sin nature is left alive, the new life cannot come. Many people fail to come to God because they want to make Jesus Savior of their life without making Him Lord. He cannot change them because they want to remain in sin.
Many people go to church and try to be good all their lives, but have never been born again.
Unless they repent of their sin loving nature and allow God to change them from the inside out, they will never make it to heaven or have a real relationship with God. Going to church and saying prayers are good and commendable, but they do not change who you are. God wants to change you into the image of His Son Jesus Christ. In order for this change to take place, you must be born again.