The intricacies of a serious relationship are extremely nuanced and vary wildly from couple to couple. Some may not be that outwardly affectionate towards each other, while others may expect a smooch several times per day.
But whatever the situation, each couple has a kind of operating system or mutual code that signals everything between them is where it should be.
Sometimes, it can take only the smallest change in behaviour or the subtlest shift to leave one person feeling like something's, well, a little bit off, or that a distance is growing between them.
So how do you know if your partner is checking out emotionally? And what do you do from there?
"It is an interesting topic but also quite broad. There are probably quite a variety of reasons people may feel that, and it most likely relates to what people can observe or sense in their relationship," Matt Garrett from Relationships Australia told HuffPost Australia.
"So I guess I would want to preface it with: if you notice these things, really rather than jumping to a conclusion that partner is cheating on you or something terrible is happening, check it out first."
As for potential signs, they are varied and plentiful, and according to Garrett, most probably quite subtle.
"The sort of things that come to mind and the things that present in the clinic room are things like a lack of affection, so perhaps you've noticed you don't kiss each other goodbye or hello anymore," he said.
"Or the little things you used to do for each other, he or she no longer does. This could be as simple as holding hands or linking fingers while you walk down the shopping aisle, or asking if you would like a cup of coffee when he or she is making one.
"Failing to ask how your day was is another example. If someone walks in the door and goes straight to the computer, or straight to the shower or laundry... that's a sign of a breakdown in communication.
"Other signs could be that you just noticing that they're maybe literally a bit disengaged. You might notice their concentration and mind and attention being somewhere else. I'm not necessarily suggesting it's somewhere else apart from you. But you might notice them fazing out the window or lost in thought or preoccupied when that's not usual for them."
While some of these things may seem small, Garrett said if they're a departure from your partner's usual behaviour, you may want to reach out to see if everything is okay. And it's better to do it sooner than later.
"If you notice a change in their behaviour, that's usually a sign that things have not been okay for whatever reason for some time," he said. "We try and put on our best front for our partners. If you are noticing something that's not quite right, what's going on or can we talk?
"Resentment is like rust to a relationship. This comes back to why we always encourage couples to address their issues sooner rather letting things slide.
"Once resentment enters a relationship, that's worrisome. If I'm not caring about your feelings and you even bug me by being in the room, than someone is checking out. Or worse, they've checked out already."
If you are going to ask the question, don't assume that you're not a part of the problem as well.
So while reopening the channels of communication is advisable, Garrett also said to do so carefully.
"By all means approach them in order to have the conversation, but try not to approach from the point of view of 'well I'm doing everything right, and you're doing everything wrong', or 'I'm the nice guy and they are the dickhead.'
"Be prepared to hear some feedback about your behaviour that could be surprising or hurtful.
"If you are going to ask the question, don't assume that you're not a part of the problem as well. Go in with a very generous and open mind. Of course it's perfectly possible it may have nothing to do with you, and they are distracted by work or stress or any number of other things.
"Just be careful what you're expecting to get back, because you might be a bit disappointed and a bit surprised. We always get that in the counselling room. This back and forth of 'I had no idea you were feeling that way'. 'Well you never ask!' 'Well you never tell me!' And off we go."
Garrett also pointed out you don't necessarily have to wait until you notice something is up with your partner, and that it could be beneficial to make sure you check in on a regular basis.
"We hate to think we do this but we often do take our partners for granted," he said. "Relationships need consistent work.
"Even though it feels artificial, it could be a good idea to make sure you connect with each other regularly by yourselves. Even if it's for half an hour -- just to ask 'what's happening with you?' It might be nothing but at least you have made that opportunity to check in with each other and have some alone time in this very busy world."