Do Not Fear: Consider the One Who Will Fight For You.

"I am the God of your father Abraham, do not fear." Genesis 26:24
God has made promises to those who respond to Him in faith and obedience; promises to keep them, provide for them, and in the Promised One, Jesus Christ, to save from sin and death.  In all that God has promised He has never left Himself without a witness.  Acts 14:17 says: "Nevertheless He did not leave Himself without witness, in that He did good, gave us rain from heaven and fruitful seasons, filling our hearts with food and gladness."  .
This is not merely a call of remembrance, but it is a call to think upon the moral character of God. Such a witness lets us know that all blessings come from God.  God reminds Isaac of such things because fear is a result of forgetfulness; it is the result of forgetting what God has done, it is forgetting that God is good.  By reminding Isaac of his father Abraham, and more importantly Gods covenantal faithfulness to Abraham, God is revealing the root of Isaac's fearfulness, it is forgetfulness, thoughtlessness and distrust.
The greatest enemy of fear is knowledge.  To know more about God, about His moral goodness and faithfulness, about His strength and sufficiency is the most basic fundamental of Spiritual Warfare.   If you want to grow in spiritual strength and defeat spiritual enemies like fear, engage in thoughtful consideration of the character and attributes of God, and reflect that the One who is strong and wise and faithful and sufficient is the very one who has promised to engage in the battle for your soul, and win! 
Remember the God of your Fathers, consider the record of His faithful fulfillment of every one of His promises, and trust that it is He who will fight on behalf of all who trust in him.  In fact, He has already won! So then, do not fear!