Passage
O my soul, thou hast said unto the LORD, Thou art my Lord: my goodness extendeth not to thee;
O my soul, thou hast said unto the LORD, Thou art my Lord: my goodness extendeth not to thee;
Psalms 16:1 Preserve me, O God: for in thee do I put my trust.
Psalms 16:2 O my soul, thou hast said unto the LORD, Thou art my Lord: my goodness extendeth not to thee;
Psalms 16:3 But to the saints that are in the earth, and to the excellent, in whom is all my delight.
Psalms 16:4 Their sorrows shall be multiplied that hasten after another god: their drink offerings of blood will I not offer, nor take up their names into my lips.
The verse centers on "soul", "thou", "hast", "said", "lord", and "goodness". It is saying that the verse draws attention to "soul" and "thou", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 1's "Preserve me O God for in thee..." into verse 3's "But to the saints that are in...", so "soul" and "thou" 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 "soul" and "thou" with trust shaped by these words, not by a vague optimism outside the passage.