Passage
Who forgiveth all thine iniquities, who healeth all thy diseases;
Who forgiveth all thine iniquities, who healeth all thy diseases;
Psalms 103:1 {[A Psalm] of David.} Bless Jehovah, O my soul; and all that is within me, [bless] his holy name!
Psalms 103:2 Bless Jehovah, O my soul, and forget not all his benefits:
Psalms 103:3 Who forgiveth all thine iniquities, who healeth all thy diseases;
Psalms 103:4 Who redeemeth thy life from the pit, who crowneth thee with loving-kindness and tender mercies;
Psalms 103:5 Who satisfieth thine old age with good [things]; thy youth is renewed like the eagle's.
The verse centers on "iniquities", "forgiveth", "thine", "healeth", and "diseases". It is saying that the verse draws attention to "iniquities" and "forgiveth", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 2's "Bless Jehovah O my soul and forget..." into verse 4's "Who redeemeth thy life from the pit...", so "iniquities" and "forgiveth" belong inside that flow. In Psalms context, the local focus is worship, trust, the LORD's kingship, and covenant mercy.
A plain takeaway is to answer the verse's own emphasis on "iniquities" and "forgiveth" with trust shaped by these words, not by a vague optimism outside the passage.