I believe that the hardest thing and the difference between Christianity and all other religions, is that in Christianity, we do good not to earn anything, but to express our gratitude to God for His mercy and forgiveness. Other religions teach that you do good to gain better "karma," or better "placement in heaven," or some other reward or appeasement for our deity, to make us more acceptable to him.
Those who know Jesus Christ however, understand that we cannot DO ANYTHING to improve our standing with God. We must simply accept the gift. Even within Christian circles, we hear such things as, "He is such a good man." or "He does so much for the less fortunate." But these things are ancillary. The issue is What do you do with the Cross of Jesus Christ?
As stated by Oswald Chambers in his daily devotional My Utmost for His Highest, he makes the observation that to think God has forgiven us because of His love, is a great mistake. God cannot forgive out of love for us. He can only forgive because of the great price paid by His own son Jesus Christ -- His very life blood, shed on the cross.