But this can cause people to worry excessively about certain traits that are probably totally normal.
Here are 10 traits that are often viewed as toxic or negative, but can actually be signs of a healthy relationship.
1. Letting things go unresolved
The common conception is that for a relationship to suceed, couples resolve every issue via effective communication, and that 'sweeping things under the rug' can have a toxic effect.
But, there is some suggestion that letting certain conflicts go unresolved could actually be beneficial for your relationship.
John Gottman, psychology professor and probably the closest we'll get to a scientific relationship expert, has been studying relationships for almost half a century.
According to his research, the most successful couples have persistent unresolved issues, sometimes spanning decades. The psychology behind it suggests that the attempt to resolve conflict can sometimes create more conflict, and that the successful couple accepts that some conflict is inevitable.
2. Making stupid mistakes
In every relationship, there will be times when one person commits what the other person might see as a monumental screw up. Every single person is flawed, and every partner will have irritating traits that drive the other partner up the wall.
This, however, should not be taken as a sign that your relationship is toxic and unhealthy: the key is how the mistake is dealt with.
Some people have difficulty with apologies because it can create a sense of vulnerability.
According to experts, in a healthy relationship the person will admit to the fault, or apologise for the error, and trust in the forgiving capacity of the partner.
3. Feeling attracted to others
Despite monogamy having the stranglehold on what society views as a normative relationship, feeling emotional or sexual thoughts towards those outside the relationship is not necessarily a sign that it's failing.
After the inital 18 month period of hormones, excitement and oxycotin, it can be perfectly natural to feel a physical attraction to someone else.
Rather than allowing jealousy or paranoia (actual toxic traits) to enter into your relationship, experts suggest instead accepting feelings you cannot control, and focussing on the fact that choosing not to act on them is the most important thing.
4. Hurting the other person's feelings
We're always told that if you don't have anything nice to say, don't say anything.
With the oft-repeated phrase...
Does my butt look big in this?
...it is assumed that in a healthy relationship, the partner will always answer in the negative, whatever the truth.
So one might confuse brutal honesty in a relationship, with toxic undermining of confidence.
Nevertheless, being honest and trusting of each other can actually be more healthy than preserving feelings. In a relationship, it's important to trust that one will communicate the negatives as well as the positives, and that the other will be mature enough to take it.
5. Being too similar
The saying goes:
There is a notion, widely upheld by romantic comedies of the 1990s and every Jane Austen book novel ever written, that the best relationship will involve two people who are utterly different and agree on nothing.
However, having similar opinions and values as your partner can actually contribute to a solid relationship foundation.
Having morals and life goals in common can mean helping each other accomplish these objectives, and in general having similar stances on important issues such as finance, work and children can help avoid conflict.
6. Being too different
Ironically, the opposite is also often cited as a negative relationship trait, but can actually be a sign of a functioning healthy partnership.
While it's helpful to share values, morals and life goals, being fundamentally different in character can actually create a good balance in a relationship.
Particularly with regards to harmonious cohabitating, one person's neuroses can be soothed by another's easygoing nature, or one person's ambition can inspire a change in another's laissez-faire attitude.
7. Spending time alone
Some Nicholas Sparks-esque novels might have us believe that the most successful couples do everything together, and share all their interests. So you might be mistaken for thinking that one person's desire to do things alone, or with others, is a sign of a toxic relationship.
The clichéd trope of a naggy wife resenting her husband's time at the pub or addiction to fantasy football doesn't help this misconception.
Nevertheless, having different interests and spending time alone actually contributes to good mental health and balance in a relationship.
Fear of spending time alone or trying things independently can lead to insecurity and even codependency.
Time and time again we're told that true love means accepting the other person as they are, warts and all.
Who could forget the eternally damnation of the line:
Love means never having to say you're sorry?
So criticism and judgment in a relationship are seen as signs of toxicity.
However, there's also a case to be made that being honest with each other and forcing each other to confront flaws can help actually help guide each other towards self improvement.
9. Keeping secrets
Honesty is a fundamental cornerstone in any healthy relationship.
People often understand that as having to share every single thing with a partner, keeping nothing to themselves.
However, there is also a danger in oversharing.
Bombarding your partner with information and overwhelming them with your innermost neuroses could actually contribute towards feelings of suffocation and drama.
Also, your partner probably does not need to know your every physical, biological trait - particularly the more unappealing ones.
10. Having less sex
It's undeniable that a healthy sex life is integral to many people's understanding of what constitutes a healthy relationship.
With that in mind, many worry that a decrease in frequency of sex reflects a negative trajectory in their relationship.
However, many older couples will tell you that while sexual vigour and physical intensity can wear off over time, that doesn't necessarily mean that a relationship is failing.
While it's important to keep intimacy alive, unavoidable factors like children, work stress and just getting older can all contribute to a perfectly natural slow down of your sex life.