The Bible says God accepts you where you are. If that is true, then why do I have to change?
Yes, God does accept you as and where you are. As sinners, we have no way to change ourselves for the better so that we can come to Him ready for heaven. But this does not mean that we should believe that God does not require a change of heart. He does not leave us where He found us.
“The religion of Christ never degrades the receiver; it ennobles and elevates. Upon certain conditions we are assured that we may become members of the royal family, children of the heavenly King. … Through faith in Christ, and obedience to the requirements of His law, we are offered a life that shall run parallel with the life of God.” The Review and Herald, May 5, 1891
“Transformation of heart means an entire change of the entire man. ‘Except a man be born again, he cannot see the kingdom of God,’ Christ declared (John 3:3). This change of heart is unseen; for it is an inward work, and yet, it is seen, because it works outward from within.
“Has the leaven of truth been at work in your heart? Has it absorbed the whole heart, the whole affections by its sanctifying power? …
“Our first work is with our own hearts. The true principles of reform should be practiced. The heart must be converted and sanctified else we have no connection with Christ.” This Day With God, 48
“When Jesus speaks of the new heart, He means the mind, the life, the whole being. To have a change of heart is to withdraw the affections from the world, and fasten them upon Christ. To have a new heart is to have a new mind, new purposes, new motives. What is the sign of a new heart?—A changed life.” Our High Calling, 159
“Purge me with hyssop, and I shall be clean; wash me, and I shall be whiter than snow. Hide Your face from my sins, and blot out all my iniquities. Create in me a clean heart, O God, and renew a steadfast spirit within me. Do not cast me away from Your presence, and do not take Your Holy Spirit from me.” Psalm 51:7, 9–11