All the Luther’s work and protest are based on three principles:

Word Alone
The Holy Scripture is the Word of God inspired and written to teach us. The main teaching of the Bible, which is the Holy Scripture, is this: “God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life” (John 3:16 NIV).

Grace Alone
God’s grace announced clearly by Luther is not something we could find in one person or where else. It is the grace that we find only in God. “The grace of God had reveled himself to all humankind”, says the Holy Bible. God, in his mercy and love, says to all humankind that Christ Jesus had suffered on behalf of all, carried to the cross the sins of all humankind and offered forgiveness and life everlasting through his blood, through his death and glorious resurrection on the third day. All of this is free, without merit of ours.

Faith Alone
All of these truths are received by faith, the one faith created in the human heart by God himself, through the Holy Spirit of God. All who stay with the promises of God and, mainly, to the forgiveness of sins offer by Christ Jesus, has the assurance that he lives with God and is full of the hope of the everlasting life. You can be a happy person and live assured that you will be with God forever if you accept there truths.