133:1 Behold, how good and how pleasant it is for brethren to dwell together in unity!
133:2 It is like the precious ointment upon the head, that ran down upon the beard, even Aaron’s beard: that went down to the skirts of his garments;
133:3 As the dew of Hermon, and as the dew that descended upon the mountains of Zion: for there the LORD commanded the blessing, even life for evermore.
The verse centers on "behold", "good", "pleasant", "brethren", "dwell", "together", "unity", and "like". It is saying that the verse draws attention to "behold" and "good", so its meaning should be read from those terms before moving to application.
The local KJV text gives this verse as the immediate unit, so "behold" and "good" carries the first interpretive weight. 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 "behold" and "good" with trust shaped by these words, not by a vague optimism outside the passage.