There is a universally-accepted custom amongst Jewish communities to recite Psalm 27 "The Lord is my light and my salvation" twice a day from the beginning of the month of Elul until until Shmini Atzetet.
This Psalm has two parts, with each one having its own distinct theme. At the beginning of the Psalm, the poet creates the impression that his trust in God causes him to be unafraid. "When evildoers draw near to me … they stumbled and fell" and even more so "If a camp encamps against me, my heart shall not fear."
King David has just one request – to dwell in the house of God all his life and to be ensconced in the tent of God. Even under the present circumstances, when he has to fight his enemies, he is confident that God will protect him and lead him to victory: "And now, my head will be raised over my enemies around me, and I will sacrifice in His tent sacrifices with joyous song."
The tone in the second half of the Psalm is completely different. The sense of confidence from the first half are replaced by fear and terror: "Hear, O Lord, to my voice which I call out…Do not hide Your presence from me; do not turn Your servant away." Instead of unconditional confidence: "If a camp encamps against me, my heart shall not fear", David is suddenly afraid of his enemies and asks of God "Do not deliver me to the desires of my adversaries". This half ends with David giving himself encouragement and confidence: "Hope for the Lord, be strong and He will give your heart courage, and hope for the Lord."
From this Psalm, we may learn about the appropriate state of mind in which we should approach the Days of Judgment and Forgiveness. On the one hand – these are Days of Judgment. We blow the Shofar and allude to the verse in Amos: "Will a shofar be sounded in the city and the people not quake?" (3:6). Each and every person trembles and fears the Holy Day of Judgment during which everyone passes before God like flock before a shepherd and He decides their fate – who will live and who will die. It is only natural then, that the very mention of the word Elul sends shivers of fear through a Jew's body, a sense of foreboding as we approach the Ruler of the world who sits in judgment.
On the other hand, we are confident that we will be judged favorably. As we tremble in fear and beg of God "Do not hide Your presence from me", we are fully confident that "The Lord is the stronghold of my life; from whom shall I be frightened?"