Passage
In this we know that we are of the truth and in his sight shall persuade our hearts.
1 John 3:19 (DRB)
Nearby Context
1 John 3:17 He that hath the substance of this world and shall see his brother in need and shall shut up his bowels from him: how doth the charity of God abide in him?
1 John 3:18 My little children, let us not love in word nor in tongue, but in deed and in truth.
1 John 3:19 In this we know that we are of the truth and in his sight shall persuade our hearts.
1 John 3:20 For if our heart reprehend us, God is greater than our heart and knoweth all things.
1 John 3:21 Dearly beloved, if our heart do not reprehend us, we have confidence towards God.
Study Lenses
The verse centers on "truth", "sight", "shall", "persuade", and "hearts". It is saying that the verse draws attention to "truth" and "sight", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 18's "My little children let us not love..." into verse 20's "For if our heart reprehend us God...", so "truth" and "sight" belong inside that flow. In 1 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "truth" and "sight" with trust shaped by these words, not by a vague optimism outside the passage.