Passage
For thou hast given me, O Lord, a delight in thy doings: and in the works of thy hands I shall rejoice.
For thou hast given me, O Lord, a delight in thy doings: and in the works of thy hands I shall rejoice.
Psalms 91:3 To shew forth thy mercy in the morning, and thy truth in the night:
Psalms 91:4 Upon an instrument of ten strings, upon the psaltery: with a canticle upon the harp.
Psalms 91:5 For thou hast given me, O Lord, a delight in thy doings: and in the works of thy hands I shall rejoice.
Psalms 91:6 O Lord, how great are thy works! thy thoughts are exceeding deep.
Psalms 91:7 The senseless man shall not know: nor will the fool understand these things.
The verse centers on "light", "thou", "hast", "given", "lord", "delight", "doings", and "works". It is saying that the verse draws attention to "light" and "thou", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 4's "Upon an instrument of ten strings upon..." into verse 6's "O Lord how great are thy works...", so "light" 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 "light" and "thou" with trust shaped by these words, not by a vague optimism outside the passage.