The last thing that dwells in your mind is what your mind digests thru the course of the evening.
What is imagined before unconsciousness covers is what will dominate one’s subconsciousness for the rest of the night.
I think this is why pPsalm 1 exhorts to meditate the word day and night. This is psychological and mental.
If you watch bad news report in the evening, you will wake up less refreshed.
Whatsoever things are honest, true, good report, think on these. Think good. Sleep good. Wake up good.