All Scripture, including the doctrine of election, is written for us, not to be driven to despair, but to have hope...

This eternal election or ordination of God to eternal life must not be considered in God's secret, mysterious counsel in a simple-minded way.  It is not as though election included nothing further, or nothing more belonged to it, or nothing more were to be considered in it, that that God foresaw who and how many were to be saved and who and how many were to be damned.  Nor should we think that He only held a sort of military muster, such as, "This one shall be saved, that one shall be damned; this one shall remain steadfast in faith to the end, that one shall not remain steadfast."

From this notion many get and imagine strange, dangerous, and deadly thoughts.  These cause and strengthen either self-confidence and lack of repentance or hopelessness and despair.  So people fall into troublesome thoughts, and say, "Before the foundation of the world was laid" (Ephesians 1:4), God has foreknown His elect to salvation.  And God's foreknowledge cannot fail or be hindered or changed by anyone.  In view of this, if I am elected to salvation, nothing can hurt me, even if I perform all sorts of shameful sins without repentance, have no regard for the Word and Sacraments, concern myself neither with repentance, faith, prayer, or godliness.  I will and must still be saved, because God's foreknowledge must come to pass. If, however, I am not foreknown, nothing helps me anyway, even though I busy myself with the Word, repent, believe, and so on.  For I cannot hinder or change God's foreknowledge."

In fact, even when godly hearts have repentance, faith, and good intentions to live by God's grace in a godly way, thoughts like these arise:  "If you are not foreknown from eternity to salvation, your every effort and entire labor is no help."  This happens especially when they see their weakness and the examples of those who have not persevered, but have fallen away again.

Against this false delusion and thought we should set up the following clear argument, which is sure and cannot fail:  All Scripture is inspired by God.  It is not for self-confidence and lack of repentance, but "for reproof, for correction, and for training in righteousness" (2 Timothy 3:16).  Also, everything in God's Word has been written for us, not so that we should be driven to despair by it, but so that "through the encouragement of Scriptures we might have hope" (Romans 15:4).  Therefore, there is no question that lack of repentance or despair should not in any way be caused or strengthened by the sound sense or right use of this teaching about God's eternal foreknowledge.  The Scriptures teach this doctrine only to direct us to the Word to encourage repentance and godliness, and to strengthen faith and assure us of our salvation.
~BOC, FSD, XI, 9-12