If we had to be perfect to enter heaven, heaven would be an empty place! Jesus's sacrifice on the cross with his shed blood made us perfect in His sight. It forgives all our imperfections, past and future. Of course we still have to keep trying to live according to His teachings and not purposefully sin, but we will at times. We acknowledge this and ask God for forgiveness, and keep trying :) This is my belief and it is Scriptural.