As Dr Tatkin explains, the killer instinct and "negativity bias" that each of our brains are built on can rear their heads in every interaction we have, but we're less likely to be able to consistently suppress them while in a close romantic relationship. This happens when we stop thinking and considering every move, and our interactions become automated.
"Everything we do, we learn, is like bicycle riding, and that includes relationships. So while at the beginning every move is considered, after a while automation takes over," Dr Tatkin says.
"Automation happens fairly soon in the beginning of a relationship because before that kicks in we are addicted to the person, we feel like we're on drugs that override everything else.
"After that we get on each others nerves because, really, all people are annoying and difficult, but there's a line that can be crossed, and when we cross that line from annoying to threatening, that's something that becomes a problem."
Dr Tatkin says while automation is good for most things we do, it's not a good thing for relationships because it means we stop thinking and let the primal, animal part of our brains take over.
"The invention of religion an social contracts is a way to get around that in society, so that people get along without killing each other," he explains.
"Since a couple is the smallest unit of society you can have, they also have to come up with the same ideas, they have to come up with the shared principles of governance so that they don't kill each other."
So in order to outsmart our always automating animal brains, Dr Tatkin says it's important, even essential, that people in a relationship develop some understanding of how their and their partner's brains work.
"Everyone is listening to all sorts of voices in the atmosphere and most of them are misleading and it would help if people understood what is normal and forgivable instead of pathologising and blaming, but also becoming better at being a human being," he says.
"Without being sappy, these all go towards loving people rather than disliking them."
According to Dr Tatkin, the only way around wanting to be at each other's throats is with presence and attention.
He says when (not if) you get into a disagreement with your partner, you should discuss it face-to-face and eye-to-eye at a relatively close distance.
One must always remain friendly or express friendliness even in the middle of a fight, and be committed to taking care of yourself and taking care of each other at the same time.
"We go eye-to-eye, face-to-face, because we are visual animals - the only way to crack each other is to look in the other's eyes," Dr Tatkin says.
"When you see mammals rough and tumble in play, they're always locking eyes with one another, but when they're at war, they're not."
And, he says, it's important to remember not to be too hard on ourselves or our partners when we get on each others nerves.
"It's important to remember that as a species we hate anything we can't handle, and in a relationship we start to realise, even though I picked you, there are parts of you that I hate and I still can't manage them. That's always going to happen."
