You don’t have to read a million books and online blogs to find out the secrets to a happy marriage. Instead, here are proven relationship lessons from scientists!

#1: Marry your money twin. University of Michigan researchers analyzed more than 1,000 couples and found that most people marry their financial opposite.  But a saver and a spender usually aren’t a lasting love match. Because studies show that the number one source of tension in a relationship is money. So even if a spendthrift marries another spendthrift – they may go into debt – but they’ll go into debt together with fewer arguments and resentment.

Another scientifically proven secret to a lasting relationship: Say “Thank you” – a lot! An Arizona State University study discovered that a lot of couples appreciate the help and chores their partner does – but show zero gratitude. But the study found that people who feel appreciated by their partner were drastically happier with their relationship.

And, the final secret to a lasting relationship straight from scientists: Work at it! Researchers studied 3,000 couples ranging from new relationships to marriages that had lasted at least 20 years and had them complete a survey about how much they loved their partner. The result? A lot of couples were still madly in love with their long-term partners even the 20-year-plus ones! And they all reported that the key to keeping that loving feeling is spending time on their relationship.  And working out issues and conflicts from the get go – instead of ignoring them and letting resentment build.