Want a love that lasts? There some Do's and Don't's you should follow, reveal clinical psychologists John and Julie Gottman          This is your happy couple's handbook: Tips and tricks for a fulfilling relationship. — CNBC file

What makes love ever-lasting? This is the topic of clinical psychologists John and Julie Gottman.

The duo have spent decades researching the topic. They interviewed over 3,000 couples. They followed some couples for even up to 20 years.

After long years of research, Gottman said that there is no set formula for a long-lasting partnership. However, he said that happy couples share certain traits that give their relationship a firm foundation.

They say the foremost quality of good couples is their ability to "make repairs.” It means that they readily acknowledge and apologise for mistakes, rather than letting them simmer.

"The couples who really were successful a few years down the road were the ones who made repairs," Julie Gottman said.  

"They made repairs when their partner didn't receive a bid for a connection. They made repairs if they said the wrong thing, [if] they blurted out the wrong thing."

You do not need to buy flowers or arrange an expensive dinner for your spouse. Just a kind comment is more than enough.

Giving an example from one of his clients, John Gottman said, "One guy said, 'Well now that we've destroyed each other's personalities, how about a piece of cheesecake.'"

Another must-have factor is that you have positive expression, particularly during conflicts. The Gottmans ask their clients to resolve their issues in 15 minutes.

They also found that there should be at least five positive interactions they should have. They suggest couples maintain a 5:1 ratio of positive to negative interactions during conflicts

Another powerful factor they suggest couples have is to avoid red flag phrases. The Gottmans ask couples to communicate openly and honestly instead of criticising their partner.

"These red flag phrases alert us that a couple is in shaky territory," The Gottmans write in their book "The Love Prescription: 7 Days to More Intimacy, Connection, and Joy." "The negative perspective might be starting to set in."