Getting into a new relationship can happen quite easily, but figuring out whether or not your partner is going to be around for a long time is another story altogether.
Research carried out by University of British Columbia economist John Helliwell found that one specific factor was the most important for a couple's satisfaction.
The study, which was carried out on thousands of couples in relation to marriage and happiness, found that the most important factor was whether or not the both partners saw each other as best friends.
After taking into consideration the couples' ages, gender, income, and health conditions, it was found that the happiest couples all said their significant other was their closest friend.
Helliwell told the New York Times: "Maybe what is really important is friendship, and to never forget that in the push and pull of daily life."
The results of the study showed that couples living together who were best friends, without being married, had the highest self-esteem and overall happiness.
It also revealed that, although women benefit more from being married to their best friend than men, women are less likely to regard their spouse as their best friend.