For this reason, if I come, I will bring to remembrance his deeds which he does, unjustly disparaging us with wicked words. And not satisfied with this, he himself does not welcome the brothers either, and he forbids those who want to do so and puts them out of the church.
3 John 1:8 Therefore we ought to support such men, so that we may be fellow workers with the truth.
3 John 1:9 I wrote something to the church, but Diotrephes, who loves to be first among them, does not welcome what we say.
3 John 1:10 For this reason, if I come, I will bring to remembrance his deeds which he does, unjustly disparaging us with wicked words. And not satisfied with this, he himself does not welcome the brothers either, and he forbids those who want to do so and puts them out of the church.
3 John 1:11 Beloved, do not imitate what is evil, but what is good. The one who does good is of God; the one who does evil has not seen God.
3 John 1:12 Demetrius has received a good witness from everyone, and from the truth itself; and we add our witness, and you know that our witness is true.
The verse centers on "reason", "come", "bring", "remembrance", "deeds", "does", "unjustly", and "disparaging". It is saying that the verse draws attention to "reason" and "come", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 9's "I wrote something to the church but..." into verse 11's "Beloved do not imitate what is evil...", so "reason" and "come" belong inside that flow. In 3 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "reason" and "come" with trust shaped by these words, not by a vague optimism outside the passage.