Paul's concern for the growing and persecuted church in Thessalonica was heartfelt, like that of a parent for their child (1 Thessalonians 2:11). It was not wrong, nor a sign of Paul's lack of confidence in God: it was the evidence of loving responsibility. The apostle was accountable to God for that church, and Paul wanted to do whatever he could to support and encourage the believers there.
 
Having left the city as it was no longer safe, he had to decide whether or not to go back. But the Lord did not let him return: the gospel still had to be preached in more cities while there was still opportunity. So Paul and Silas sent Timothy. He was a trusted pastor and teacher, well gifted to encourage and stabilise the church as it faced opposition. And Paul did not pretend that the trials were nothing. They were real and would have some painful effects. Triumphalism and the prosperity gospel did not live in Thessalonica, because true faith in Christ involves both believing in Christ and suffering for Him (Philippians 1:29).
 
And yet Satan can tempt us to give up or run away when trouble comes. So Paul's spiritual pastoral instinct was to encourage them to be strong in Christ. Timothy's role was to teach them the gospel truths and encourage them to live out an authentic Christ-like life despite hostility. It was not that Paul did not trust them, he simply wanted Timothy to support them so that they would remain true to Christ.
 
It is right to be concerned for brothers and sisters who are going through difficult circumstances (2 Corinthians 11:28). Satan lies about the future (John 8:44) and makes up frightening scenarios to prevent God's people from serving wholeheartedly. So we all need that pastoral care from the Lord and His under-shepherds. The basis of pastoral care is not human sympathy but heavenly strengthening through God's Word, applied to our situation and countering the natural reactions of our hearts. Bible-based faith will always grow when it is tested.