Serotonin
Supplement
Discussed as a neurotransmitter that influences the ability to delay gratification, and is involved in various mental events, not exclusively emotion.
Mentioned in 2 videos
Videos Mentioning Serotonin

Lisa Feldman Barrett: How the Brain Creates Emotions | MIT Artificial General Intelligence (AGI)
Lex Fridman
Discussed as a neurotransmitter that influences the ability to delay gratification, and is involved in various mental events, not exclusively emotion.

How Your Brain Works & Changes | Huberman Lab Essentials
Andrew Huberman
A neuromodulator that, when released, tends to make individuals feel content with their current situation and resources.