Whenever I get in those moods, I tend to get pretty lethargic because it's tiring.
This song is from a kids show, sure, but it's very well done. The extended version tends to put me to sleep.
Otherwise, sometimes György Ligeti is nice, like 'Lux Aeterna'. It's good background music, also helps me sleep.
That's the common denominator, really - Relaxing.
I'll list the genres for taste.
This song I listen to when sad only it is on Youtube. It won't play full son on the site even I listen to it on spotify.
1.Dignity Malumi (kinda pop like)
2. Deadman Glasslands (rock)
3. Lowly Wolves at the gates (rock)
4. Rainy days Late night Alumni (soft)