9/20/2026
This is the fifth piece about David Phillips’s book High on Life: How to Naturally Harness the Power of Six Hormones and Revolutionize Yourself.
Today I'll talk about another chemical in Phillips's framework: serotonin (血清素), sometimes described as a chemical associated with mood stability and well-being.
Serotonin is both a neurotransmitter and a signaling molecule in the body. Most of the body's serotonin is produced outside the brain, particularly in the gastrointestinal tract, while serotonin in the brain is produced by specialized neurons.
Serotonin is involved in many functions, including:
Mood and emotional regulation
It is involved in regulating mood, anxiety, and emotional responses and is associated with feelings of calm and contentment.Sleep and the body clock
Serotonin is a precursor to melatonin and participates in the regulation of sleep and circadian rhythms.Appetite and digestion
Serotonin plays an important role in gastrointestinal movement and appetite-related signaling.Impulse control
Serotonin is involved in regulating impulsive behavior and emotional responses.Pain regulation
It also participates in the body's complex system for modulating pain.
One way I think about the difference between dopamine and serotonin is this:
Dopamine asks, “What else do I want?”
Serotonin is closer to, “I'm okay with where I am and what I have.”
Dopamine can push us toward the next goal, the next achievement, or the next reward. Serotonin is more associated with a stable sense of well-being and contentment.
Imagine that all your friends have achieved something that you haven't. They have advanced further in their careers, bought something you cannot afford, or invested in a stock that made them money.
You look at your own situation calmly and say, That's their path. I'll continue doing what makes sense for me. You are what people say in Chinese, 不攀比 (bù pān bǐ), don't measure yourself against others.
That ability to remain relatively steady rather than constantly chasing what others have is a valuable form of emotional stability.
So how can we support the body's serotonin system?
One simple suggestion Phillips discusses is exposure to natural light. Research has found links between daylight exposure, serotonin-related activity, and circadian regulation. This is one reason getting outside during the day can be a useful habit, particularly when we are feeling sluggish or low.
Instead of leaving it to chance, you can simply put daylight into your schedule.
A quick summary so far
Dopamine: I want to do it!
Testosterone: I dare to do it!
Endorphins: That hurts, but I can get through it.
Oxytocin: I feel close and safe with you.
Serotonin: I'm calm. I have enough.
Perhaps that's why serotonin is such an interesting part of this series.
We spend a great deal of our lives trying to get somewhere: more money, more achievement, more recognition, more experiences.
But a good life cannot consist entirely of wanting more.
Sometimes the goal is not to climb higher. It is to be able to stop for a moment, look around, and feel that where you are is enough.
