Passage
Thou knowest my sitting and my rising: thou vnderstandest my thought afarre off.
Thou knowest my sitting and my rising: thou vnderstandest my thought afarre off.
Psalms 139:1 To him that excelleth. A Psalme of David. O Lord, thou hast tried me and knowen me.
Psalms 139:2 Thou knowest my sitting and my rising: thou vnderstandest my thought afarre off.
Psalms 139:3 Thou compassest my pathes, and my lying downe, and art accustomed to all my wayes.
Psalms 139:4 For there is not a word in my tongue, but loe, thou knowest it wholy, O Lord.
The verse centers on "thou", "knowest", "sitting", "rising", "vnderstandest", "thought", and "afarre". It is saying that the verse draws attention to "thou" and "knowest", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 1's "To him that excelleth A Psalme of..." into verse 3's "Thou compassest my pathes and my lying...", so "thou" and "knowest" 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 "thou" and "knowest" with trust shaped by these words, not by a vague optimism outside the passage.