Therapists from California State University, Northridge and Virginia Tech say accepting these problems is better than striving for perfection.

And they blame cultural fairytales and modern love stories for perpetuating the myth that enjoying a perfect relationship is possible.

"The field of mental health perpetuates this myth with the very concept of "mental health," which implies a state without suffering," they say.

Mrs Nadine Field, a consultant psychologist, said it was a "fantasy" that any relationship could be perfect and that striving for such an impossible state could lead to bitter disappointment.

She said this disappointment could then cause people to focus on the negative aspects of a relationship, and lead to more disappointment and resentment.