Everyone has disagreed with their significant other at some time or another. (And if you haven't, don't feel too smug -- you will.)
After all, entering a serious relationship is basically a process whereby two previously independent individuals become a single unit. Unless you're both robots, of course there are going to be differences in opinion along the way.
While the frequency and nature of these disagreements will vary from couple to couple (and in terms of what's okay and what's not), there are certain topics or issues in every relationship more likely to cause a flare-up than others.
The Huffington Post Australia spoke to psychologist and Clinical Director of Relationships Australia NSW, Elisabeth Shaw, to find out the most common reasons most couples fight... and how you can work to avoid those 'same-old' arguments in the future.
Surprise, surprise. One of the most common catalysts for arguments in a relationship is the management (or mismanagement) of finances.
"For many couples, the meaning they attach to certain [financial issues] is more damaging than the issues themselves," Shaw told The Huffington Post Australia.
"For instance, if I was to interpret a partner's separate bank account as a sign he or she wasn't committed to me, it could be very distressing.
"But if I thought, 'it doesn't mean anything, I'm glad I have one too,' then it's not an issue."
According to Shaw, money can be a tricky topic for many as people don't want to pigeonhole themselves as a certain 'type' when it comes to how they manage their expenses.
Fighting over financial issues really has to do with the evolution of the relationship and whether you're brave enough to have that discussion early on.
"Interestingly, most couples are happy to discuss money if it's about forward planning. You know, 'we'd like to buy this sort of house', that kind of thing," Shaw said.
"Where they run into great difficulty is discussing the hard everyday stuff, such as 'you haven't been putting as much in the joint account as me' or 'you're a spendthrift'.
"Generally people hate to discuss it because they don't like feeling like a tight-arse."
One of the main reasons money continues to be a bone of contention between couples is because they don't discuss their financial habits prior to committing to one another, Shaw says.
"Often people don't discuss their financial style before getting involved," she told HuffPost Australia. "You do need to be careful in some instances -- you don't want to fall victim to sexually transmitted debt.
"How you view somebody's spending habits might also change as the relationship progresses. When you are dating someone and you go out and they shout everyone drinks, you might be thinking, 'how lovely, how generous, how great'. Once you move in together, this way of thinking might change to 'oh gosh, that's our new couch'.
"Fighting over financial issues really has to do with the evolution of the relationship and whether you're brave enough to have that discussion early on."
Ah yes, the good old in-laws. According to Shaw, how to manage your partner's family (and vice versa) can be particularly problematic if the two of you come from different relationship backgrounds.
"If one person comes from a family with a close and rewarding relationship, who like to see their family a lot and are used to a lot of family contact, and the other person's family has much looser connections with no regular routine of catching up, this can result in some differences of opinion," Shaw said.
"And this is likely to get worse if the two of you have children, because family involvement does tend to intensify after that.
"Then you have the questions of 'where do we spend Christmas?' as well as how much involvement you want from each family in terms of their involvement with your children.
"The problem is there are so many people in the arrangement. There's not only what you want and what your partner wants, but what your in-laws want, who your children are attached to, and so on. It can become very fraught."
Togetherness vs. separateness
"There are some running themes for couples and one of the most common is the negotiation of separateness and togetherness," Shaw told HuffPost Australia. "This plays out in lots of ways, but it can be very much about how much time we have to ourselves versus the time you spend together.
"If you're really committed, you might expect you spend all your time together. Anything the other person does without you -- even masturbation -- can be viewed as robbing the relationship of focus and be considered as a threat.
"Couples that work well together are able to negotiate the idea of 'together' versus 'separate' time without taking it personally. It's important to be able to negotiate a healthy balance between the two things, because you do need to be able to be separate. You want to be able to go to work, go to the gym and live your life."
Do not assume your partner will or won't do a particular thing just because your relationship is progressing.
"The amount of people I see who say, 'well I assumed when we got married, you would stop drinking' or something similar is just astounding," Shaw said. "They don't mention the issue at all, they just assume it would be the obvious step for that person to change that part of their behaviour.
"And then you have the other person saying, 'well, that's what I did when you met me, why did you think I would change?'
"I think many people get caught up in the optimism of a relationship and think because they get along well and because they love each other, their thinking is the same.
"Even at retirement I have couples saying 'well wouldn't it be obvious, when we retire we'd be doing everything together?' You need to discuss these things before you do them.
"That's not what real people do, of course, but ideally before you take the next step you'd have the discussion about what you are expecting to be the same and what you are expecting to be different."
How you fight
Interestingly, Shaw says how a couple fights can actually be one of the main things they fight about -- and one of the trickiest things to resolve.
"So, for example, say if there's an issue with money, that might be how the fight starts," Shaw said. "Then what the fight becomes about is 'I don't like how you speak to me,' or 'you don't listen to me.' You end up fighting about your fighting style."
According to Shaw, this is a particularly unhelpful form of argument because it's not dealing with the actual issue at hand.
"If people could actually develop a fighting style that worked for them, they'd find the issues they had originally often aren't so insurmountable," Shaw said. "What really annoys people is the difficulty of getting through to each other. That's actually what can really grind you down.
"The best way to manage this is to try and discuss it outside of a fight. Actually put some time aside to say, 'let's unpack how we fight. The roles we fall into, the attitudes we have. Let's see if we can unpack it and try and negotiate some rules as to how we talk'.
"A lot of it has to do with hearing each other out -- that's an enormous part of getting things right."
Call in the pros
If that doesn't work, Shaw says it might be time to consider visiting a relationship counsellor.
"A lot of people think seeing a couple counsellor equals terrible trouble and must be the kiss of death," she said.
"In reality, the couples that we see tend to say 'gee, I wish we had come earlier, we would have saved ourselves from those entanglements'.
"Sometimes just having a third person in the room can really help. People might come to me about an issue, say it's a negotiation around managing the children, but to me it will be obvious it's the style of arguing that's blocking [the solution]. How they are going about it is proving to be a bigger block than their differences with parenting.
"Having someone to hear you and diagnose where it's getting stuck, and to note the pivotal point where the conversation takes a turn for the worse... that can be extremely helpful."