Discouragement can take many different forms, but it always tends toward the same end of veiling the goodness of God from our eyes. In Psalm 42, we have the divinely-provided cure for discouragement through the experience and the inspired pen of David.
Too often our hearts are distracted from the glorious preoccupation of worshipping the Lord. The allurements of the world, the cares of life, and the pain of loss all have the tendency to pull us down into a spiral of despair and discontent. Psalm 103 calls us to speak to ourselves and call ourselves to remembrance of who God is and what He has done for us that we might be compelled to lift our eyes to the One who is worthy of all our praise.