A Christian Science perspective.
When the Psalmist wrote, "O my God, my soul is cast down within me" (Ps. 42:6), maybe things weren't going so well in his life. Perhaps the enemy was close on his heels. I've found that if I'm feeling down, I can say, like that Psalmist who trusted God beyond anything else said a few verses later, "Hope thou in God: for I shall yet praise him, who is the health of my countenance, and my God" (42:11).
Prayer to an all-powerful God can dispel depressed and defeated feelings quickly and effectively. Whether we feel cut off from God or our focus on our own problems fills us with darkness, prayer to God, who loves each of us as His dear children, can release fresh hope and encouragement. God is as close to us as He was to the Psalmist, to help us leap over hurdles. And the psalms are universal, speaking today as they did thousands of years ago, to humanity's hunger for a God of comfort.
The psalms are filled with poignant moments of sorrow, lament, and even bleakness. But often, right on the heels of those moments – as in Psalm 42 – there is confident celebrating, praising, and affirmation of the power, presence, ability, and supremacy of God to overcome all suffering. They declare that no one is ever apart from God's goodness and love.
The 23rd Psalm says, "Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me." This deep connection with God – especially in overwhelming moments – is right now available for each of us as we turn in gratitude and openness to God to receive it.