(1) Thanksgiving for Sanctification
We ought always to give thanks to God for you, brothers, as is right, because your faith is growing abundantly, and the love of every one of you for one another is increasing. Therefore we ourselves boast about you in the churches of God for your stead fastness and faith in all your persecutions and in the afflictions that you are enduring. (2 Thess. 1:3-4)
The first prayer of 2 Thessalonians is thanksgiving for sanctification. We learn in verse 4 that the Thessalonian church is enduring persecutions and afflictions. But in the midst of their trials (and perhaps because of them), their faith is growing and their love for one another is increasing. Paul sees this not as a work of the Thessalonians, but of God . He says, "We ought always to give thanks to God." What I take from this is that when a Christian sees his brother growing in Christ, he should thank the Lord for His sanctifying work. And this prayer is not meant to be prayed every so often, but always. So, the first application I get from 2 Thessalonians is:
Christians should, in their daily prayers, thank God for His work in their brothers' lives.