Two research backed tips for a happy marriage:

First: A study from March 2016 conducted by a professor at Florida State tracked 135 couples for four years soon after they were married. The study found that couples with higher expectations about marriage tended to be less happy and satisfied with their marriages and more likely to have failed marriages than those couples with lower marital expectations. Thus, a conclusion of the study was a possible key to marital bliss is to lower your expectations. Link to study: Marriage Study – Lower Expectations

Second (and my favorite): Researchers have found a simple formula is effective in predicting successful marriages:

Frequency of Lovemaking – Frequency of Quarrels = X 

X being positive was strongly associated with successful marriages and a negative X value often was predictive of failure/unhappiness in marriage.

Note that correlation does not equal causation and as such researchers noted that “it does not follow that we can increase marital happiness of people who argue a lot by encouraging them to have intercourse more often–but it would be an interesting technique to try.” Link to study: Linear Prediction of Marital Happiness