Passage
For the truth’s sake, which dwelleth in us, and shall be with us for ever.
For the truth’s sake, which dwelleth in us, and shall be with us for ever.
2 John 1:1 The elder unto the elect lady and her children, whom I love in the truth; and not I only, but also all they that have known the truth;
2 John 1:2 For the truth’s sake, which dwelleth in us, and shall be with us for ever.
2 John 1:3 Grace be with you, mercy, and peace, from God the Father, and from the Lord Jesus Christ, the Son of the Father, in truth and love.
2 John 1:4 I rejoiced greatly that I found of thy children walking in truth, as we have received a commandment from the Father.
The verse centers on "truth", "sake", "dwelleth", "shall", and "ever". It is saying that the verse draws attention to "truth" and "sake", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 1's "The elder unto the elect lady and..." into verse 3's "Grace be with you mercy and peace...", so "truth" and "sake" belong inside that flow. In 2 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "truth" and "sake" with trust shaped by these words, not by a vague optimism outside the passage.