St. Paul, in today's first reading, had to address panic, not at the disco, but in Thessalonica. His evangelizing of that area had been cut short, so he had been unable to stay there and model Christian living for those people, just converted from the old Greek and Roman gods. Some expected the Lord to come so soon that they could just retire in ease, while others were startled by any and every whisper about the end of time. Paul took care of the first group with his "no work, no eat" policy. With the second, he reminded them not to pay attention to rumors and unauthentic letters claiming to foretell the future.
Even now there are many prophets scaring the daylights out of the devout with talk of chastisement and doom. Paul reminds us, too, the Day of the Lord will come like a thief in the night. That doesn't mean we should keep vigil by our doors and windows; it means to live in the Lord's presence all the time!