The Science Of Why The Honeymoon Phase Ends, And The Neuropeptide That Blocks Romantic Chemistry
Chemistry can last a lifetime when you eliminate just one single ingredient.
Diego Cervo via Shutterstock We have all heard it: “The honeymoon phase does not last”.
It is one of the most recycled myths about relationships, whispered at weddings, repeated in therapy, and passed down like a universal truth. Supposedly, the spark burns out in about two years, and what you are left with is companionship rather than passion.
That story is wrong.
Trailblazing anthropologist Helen Fisher shook the world years ago with research showing that early-stage romantic passion lights up the brain like a drug but fades after about two years. It was groundbreaking work, but the message was discouraging. Enjoy it while it lasts, because it will not, was the message.
Then came Genetic Energetics, which revealed that chemistry does not automatically expire. GE discovered what actually ignites the chemical storm of attraction: vibrational alignment with the opposite-gender parent’s energetic blueprint.
That adage that men are attracted to women like their mother and women are attracted to men like their father turns out to be true, not because of psychology or habit, but because of genetically coded frequencies. And for the queer population, the same principle applies. Partners are drawn to mates who carry the same genetic frequency as their opposite-gender parent.
The honeymoon phase ends because of one single ingredient: Substance P
This explained why chemistry sparks instantly and why it feels so powerful. Yet the reason it sometimes left abruptly, or seemed to vanish altogether, was still a mystery. We knew it was not simply the passage of time. We also knew it never fully disappeared. Something was suppressing it.
The unknown became a constant, nagging puzzle for me, as founder of GE. It was nearly 15 years later when the Institute uncovered the answer. The one single ingredient that can shut chemistry down is pain, and the chemical that delivers its message is a little-known neuropeptide called Substance P.
The real chemistry soup
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Here is what actually fuels attraction and passion:
- PEA (phenylethylamine): the infatuation spark that makes you feel high
- Dopamine: the reward loop that keeps you coming back for more
- Oxytocin: the bonding molecule that makes you feel safe and close
- Serotonin: the mood regulator that keeps things steady
- Norepinephrine: the butterflies in your stomach and the hyper-focus
- Testosterone: the sexual drive and physical confidence
Together, these chemicals create the rush of attraction.
But there is another player that explains why passion sometimes crashes.
The wildcard: Substance P
Substance P is a neuropeptide. It does not deliver pleasure. It delivers pain. And when it gets triggered, everything changes.
When Substance P spikes, it hijacks the entire system:
- It dulls dopamine’s thrill, so nothing feels exciting anymore.
- It extinguishes PEA’s spark, leaving the rush of infatuation flat.
- It destabilizes serotonin, and your moods crash.
- It flips norepinephrine from butterflies to anxiety.
- It shuts down oxytocin and testosterone, erasing bonding and desire.
Suddenly, what felt magnetic just months ago can feel empty or even repellent. Not because time killed the spark, but because pain chemically blocked it.
The good news
Here is the breakthrough. We now know chemistry is not one-size-fits-all.
For some couples, it is instant. They meet, the brain chemistry floods, and the attraction feels undeniable. For others, it is gradual. The chemistry builds naturally over time as emotional and physical alignment grows. Both are real. Both are valid.
This is wonderful news. If you have never felt that lightning-strike attraction, you are not broken. Chemistry can develop over time, and when it does, it can be just as powerful. If you have felt that instant rush, but it seemed to fade just as quickly, you now know where to look first. The culprit is almost always pain—emotional or energetic distress you could not see at first because the brain chemicals made everything feel like a drug.
Either way, the truth is the same. Chemistry is not fragile. It does not expire. It only shuts down when pain activates Substance P.
And here is the best part. When the pain is resolved, the chemistry comes back. Instantly for some, gradually for others, but always reliably. The thrill, the spark, the butterflies, the desire—all of it returns.
No tricks required
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What makes this so refreshing is that you do not need clever tricks, hacks, or gimmicks to rekindle passion. You already know how. The answer is simple: eliminate the one single ingredient that blocks it—pain.
If you are engaging a professional therapist, a relationship coach, or even a healer, make sure they know about Substance P. If they don’t, please ask them to do their own research about the emotional and physical effects of this one neuropeptide, and get back to you when they have a more complete understanding of how our bodies and minds respond to pain. This is a game-changer for coaches and therapists. They already know they need to help their clients out of pain and discomfort. What most of them do not yet realize is just how profound that need is.
Do this, and chemistry does not just return. It can last a lifetime.
The lifelong attraction secret
Note this: to the degree that Substance P is activated, the pain needs to be resolved. If it is physical, resolution is often straightforward. Scratches, bruises, and even broken bones will usually heal. Emotional pain is trickier. It can come from many places: Genetic Energetic differences, childhood wounds, ancestral history, mismatched values, or divergent life missions.
This is where experienced relationship professionals have so much to offer. They can help couples identify, understand, and resolve the root of emotional distress so Substance P no longer hijacks the chemistry system.
For this article, the big win is simple. Chemistry and attraction are here to stay and can last a lifetime. Stay emotionally healthy and physically happy, and your relationship will be gifted with an extra dose of brain chemistry that makes everything even better.
Chemistry is not fragile. It is evergreen when you eliminate the one single ingredient that blocks it.
That is the real secret to lifelong passion.
Larry Michel is a relationship coach & founder of the Institute of Genetic Energetics and author of LASTING: 11 Illuminations & Essential Questions for a Co-Creative Evolutionary Partnership. Larry’s science uncovers how people's unique genetic coding drives every relationship decision, including who they're drawn to as partners.
