Passage
all things prove; that which is good hold fast;
all things prove; that which is good hold fast;
1 Thessalonians 5:19 The Spirit quench not;
1 Thessalonians 5:20 prophesyings despise not;
1 Thessalonians 5:21 all things prove; that which is good hold fast;
1 Thessalonians 5:22 from all appearance of evil abstain ye;
1 Thessalonians 5:23 and the God of the peace Himself sanctify you wholly, and may your whole spirit, and soul, and body, be preserved unblameably in the presence of our Lord Jesus Christ;
The verse centers on "all things", "prove", "good", "hold", and "fast". It is saying that the verse draws attention to "all things" and "prove", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 20's "prophesyings despise not..." into verse 22's "from all appearance of evil abstain ye...", so "all things" and "prove" belong inside that flow. In 1 Thessalonians context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "all things" and "prove" with trust shaped by these words, not by a vague optimism outside the passage.