Summary: Give thanks for: 1) God Himself (Ps.103:1), 2) God's Benefits (Ps. 103:2), 3) God's Forgiveness and Healing (Ps. 103:3), 4) God's Redemption, love & Mercy (Ps. 103:4), and finally: 5) God's Satisfaction & Renewal (Ps.103:5)
Psalm 103:1-5[103:1] Bless the LORD, O my soul, and all that is within me, bless his holy name!  Bless the LORD, O my soul, and forget not all his benefits,  who forgives all your iniquity, who heals all your diseases,  who redeems your life from the pit, who crowns you with steadfast love and mercy,  who satisfies you with good so that your youth is renewed like the eagle's (ESV).
It’s been said that: “All movies are mirrors, even when we don’t like what we see in it, and even when the movie isn’t particularly thoughtful about how and what it reflects. The recent release of the movie Joker reflects us, and our cultural moment, in ways we’d do well to consider. The Joker, like Satan himself, knows that humans are inherently perverse creatures, lured in by spectacle, addicted to novelty, prone to amusing ourselves to death. In this way Joker is the perfect bogeyman for our age, embodying the toxic, corrosive power of an entertainment-obsessed, hyper-mediated society of spectacle. Like most movies, it becomes a testament of human corruption with the root of sin. (https://www.thegospelcoalition.org/article/is-the-joker-on-us/)
Psalm 103 is designed to promote the blessing and exaltation of God, (while acknowledging the problem of pain, suffering, sin and death). This psalm represents a soliloquy in which David surveys God’s goodness and encourages the angels and the works of God’s creation to join him in divine praise (MacArthur, J. J. (1997). The MacArthur Study Bible (electronic ed.) (Ps 103:1). Nashville: Word Pub.). Beginning with individual thanksgiving … it was probably to be sung in a liturgical setting it was meant to inspire others —which it has done and continues to do. Eaton proposed that it was a hymn for the fall festival. (Ross, A. P. (2016). A Commentary on the Psalms (90–150): Commentary (Vol. 3, p. 228). Grand Rapids, MI: Kregel Academic.)
The only answer to the problem of pain, suffering, sin and death, is the life and work of Christ. Instead of a prideful self-satisfaction, faith in God realizes God as the source of all blessing and thankfulness is an expression of faith that appropriately responds to this realization. In our individual lives and corporate praise, it is fitting to give thanks for: 1) God Himself (Psalm 103:1), 2) God's Benefits (Psalm 103:2), 3) God's Forgiveness and Healing (Psalm 103:3), 4) God's Redemption, love & Mercy (Psalm 103:4), and finally: 5) God's Satisfaction & Renewal (Psalm 103:5).
First, we can give thanks for:
1) God Himself (Psalm 103:1)
Psalm 103:1[103:1] Bless the LORD, O my soul, and all that is within me, bless his holy name!
• “WE WILL SPEND HALF OUR TIME IN THE FIRST TWO POINTS”.
What does it mean to bless God? Bless” (barak, Heb.) is used here with the meaning “esteem greatly” or “praise” (cf. Eph. 1:3). (Criswell, W. A., Patterson, P., Clendenen, E. R., Akin, D. L., Chamberlin, M., Patterson, D. K., & Pogue, J. (Eds.). (1991). Believer’s Study Bible (electronic ed., Ps 103:1). Nashville: Thomas Nelson.) The Hebrew verb (in the piel) “always means to express solemn words that show the appreciation, gratitude, respect, joint relationship, or good will of the speaker, thus promoting respect for the one being blessed…. When God is the object, brk … (it is) rendered “praise” (Williams, D., & Ogilvie, L. J. (1989). Vol. 14: The Preacher's Commentary Series, Volume 14 : Psalms 73-150. The Preacher's Commentary series (225–226). Nashville, Tennessee: Thomas Nelson Inc.).
• When the Lord ‘blesses’ us, He reviews our needs and responds to them; when we ‘bless’ the Lord, we review His excellencies and respond to them (Carson, D. A. (1994). New Bible commentary : 21st century edition (4th ed.) (Ps 103:1–5). Leicester, England; Downers Grove, Ill., USA: Inter-Varsity Press)
Praise requires preparation. Our hearts, ever inclined to deadness and coldness, must be stirred to properly take up praise. If he was anything, David was a student of his heart. We all should be! So before he offers one word of praise, he stokes his heart. He preaches to himself (Ellsworth, R. (2006). Opening up Psalms (132). Leominster: Day One Publications.)
Please turn to Jeremiah 33
In verse one of Psalm 103, we find a singer who gives voice to the sentiments of the many gathered at the temple for a service of thanksgiving and thank offering in response to Yahweh’s benefits to them as individuals. It is a solo contribution to communal worship rather than an individual testimony. According to Jer 33:11 the theological backbone of the thanksgiving service was provided by the communal hymn:
Jeremiah 33:11 the voice of mirth and the voice of gladness, the voice of the bridegroom and the voice of the bride, the voices of those who sing, as they bring thank offerings to the house of the LORD: "'Give thanks to the LORD of hosts, for the LORD is good, for his steadfast love endures forever!' For I will restore the fortunes of the land as at first, says the LORD. (ESV)