Passage
The Lord is thy keeper: the Lord is thy shadow at thy right hand.
The Lord is thy keeper: the Lord is thy shadow at thy right hand.
Psalms 121:3 He wil not suffer thy foote to slippe: for he that keepeth thee, will not slumber.
Psalms 121:4 Beholde, he that keepeth Israel, wil neither slumber nor sleepe.
Psalms 121:5 The Lord is thy keeper: the Lord is thy shadow at thy right hand.
Psalms 121:6 The sunne shall not smite thee by day, nor the moone by night.
Psalms 121:7 The Lord shall preserue thee from all euil: he shall keepe thy soule.
The verse centers on "lord", "keeper", "shadow", "right", and "hand". It is saying that the verse draws attention to "lord" and "keeper", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 4's "Beholde he that keepeth Israel wil neither..." into verse 6's "The sunne shall not smite thee by...", so "lord" and "keeper" 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 "lord" and "keeper" with trust shaped by these words, not by a vague optimism outside the passage.