system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so much easier to stay in a bad mood than a good one?
gpt
A mild bad mood (not anything like clinical depression) is a survival response to an unfamiliar or challenging situation.  Our body is telling us to be alert, be on guard, and be attentive.

A mild good mood (that isn't clinical mania) is a signal that we are in a familiar and comfortable situation.  We don't have to stay alert because we are safe.

Humans being humans, and the modern world being the modern world, we are more likely to be uncomfortable than comfortable.  But that's okay, it's part of growth.  What we might want to do, though, is carve out a space and time to be warm and safe and comfortable.  

Curl up an hour before bed with a good book and a cup of hot tea, for example.  Or meditate or pray.  Or journal.  Or maybe just clean and organize, some people find that ritual comforting.  Listen to music.  Play with your children.  Cuddle with a loved one. 

Whatever it is, find a time and place for it in your life.  And don't beat yourself up if you are in a mild bad mood the rest of the time.  It's okay, it means you are challenging yourself, and some day the uncomfortable will feel comfortable -- at which time, it's probably time for a new challenge.