In some research that was published earlier this year, Gottman, who has been analysing relationships for more than 40 years, studied couples for the length of their relationships to understand why people break-up.
Four factors stood out to Gottman, and if a couple's relationship was overrun with these then the chances are they would divorce/break up around 6 years into their marriage. The factors were:
All partners moan about each other - from leaving the washing up to being late for dinner - but corrosive criticism (when you criticise their personality) is detrimental to a relationship, says Gottman.
For example: "You're late because you don't care about me."
This type of criticism, that suggests the other person is bad or wrong at some deeper level, "strikes at the heart of the other person".
Gottman found that having contempt for a partner was the biggest predictor of divorce.
Contempt - which includes sarcasm, name-calling, mimicking and eye-rolling - makes the other person feel worthless.
When someone consistently makes excuses for their mistakes, it can signal the end, says Gottman.
This is worse when partners try to score points off one another on top of being defensive.
This is when someone cuts off all communication - there are no attempts or effort to respond or connect with their partner.
Stonewalling can be a result of prolonged criticism, contempt and defensiveness.