A short gratitude practice before bed, even just naming a few good things from the day, appears to ease the kind of low-level worry that otherwise keeps the mind circling once the lights go out. Where anxious thoughts tend to loop, a deliberately grateful thought gives attention somewhere calmer to land.
Part of the effect seems to be about replacement rather than suppression: it is difficult to actively worry and actively appreciate at the same time, so a few minutes spent on the second tends to crowd out at least some of the first, especially in the vulnerable window right before sleep.
The practice does not need to be elaborate to help. A brief, specific recollection, something that went well, someone who was kind, a small relief, seems to do more for a settled mind than a longer, vaguer effort to feel thankful about everything at once before the eyes finally close.