I did this course someone on this subreddit recommended it's by Yale would recommend. Basically it all comes down to mood and energy.
Do I like someone? When I think of them does it bring a smile to my face and this yearning to I can't wait to see them?
Passion about something - does it make you feel energetic / enthused and leaves you happy even after the topic ends?
I have to agree for some reason sadness does wonders for creativity lmao gets you wanting to exercise it out through creative means I suppose! Another is this dip in mood and energy you feel lacklustre and don't feel as you normally do
https://www.coursera.org/learn/managing-emotions-uncertainty-stress
This is the course. It's aimed at teachers in a student teacher setting but I find it helpful still regardless, would recommend