"...confirming the souls of the disciples, encouraging them to continue in the faith, and saying that through many tribulations we must enter the kingdom of God" (Acts 14:22).
In a letter dated September 8, 1541, Luther explained to a friend named Link about the three trials experienced by the church: persecution, false teaching, and worldly-mindedness. The key is to understand that the second is worse than the first, and the third is worst of all.
"The first trial of the church (from the beginning of the world) always comes from the tyrants, who shed our blood. When the tyrants are almost at an end, the far more harmful trial brought on by heretics follows, reinforcing the violence of the tyrants. After the heretics have been somewhat suppressed, there follows the most harmful trial of all in the time of peace, namely, license and worldly-mindedness in living, life without the Law, without the Word, since we are satiated and surfeited with the Word, which is no longer necessary 'because the enemies are defeated.' So the worst enemies of a man are those of his own household."
My observation would be that today the church faces all three. The perfect storm! Still, worldly-mindedness is the worst. And that is because persecution purifies the church and leads to blessing (Matt. 5:10). False teaching, when met with the Word of God, results in a stronger confession of faith (i.e., more clear, confident, and comforting). But worldly-mindedness, unless reversed, leads only to a church no longer worthy of the name.