HAVING raised the issue of the rapture at the end of chapter 4, here Paul reminded them that the timing of end time events is secret (vs. 2 & Acts 1:7). Not that there are no indicators at all (vs. 3, Matthew 16:2-3 & Luke 12:56). Especially for believers, Paul pointed out that we should actually be able to anticipate the coming of the Lord, or at the least be constantly ready for it (vs. 4). More than once in the New Testament, we are reminded to be on the lookout for Christ's return, & to live as if His coming is imminent. Because it is (vs. 6).
Speaking of how we live, Paul closes this first letter to the Thessalonians by offering some parting shots on how we should live our lives as we wait for Christ's return. He begins his ending by reminding us that this "looking-and-living-for-Christ's-return-thing" is very serious business indeed (vs. 8). Knowing that the rapture precedes the 7 years Tribulation Period (and realizing that through the rapture Christ saves the church from having to go through that horrid time – vs. 9), we have layer upon layer of reasons to live righteously. And, Paul gives us ways to do that.